This page doesn't "explain everything there is to know" about using PcbNew to lay down tracks on a PCB design. It helps you get started with that, by continuing an simple example, contrived to skirt many "thorny issues". I will try to create other pages to deal with the matters you've been spared here.
You'll be delighted to learn, I hope, that at least for everyday needs, laying down tracks is easy… once you get the hang of the system.
In fact everything has, I believe, been "easy"… in isolation. It is just a bit daunting getting started, learning all the different bits, and learning to put them together in the right sequence. The hardest bit, I suspect, is keeping clear in your mind the difference between….
If you've got that clear, of course there's also the not so easy matter of how the schematic, via CvPcb and the netlist, "translates" to a PCB… but you can!! do it!!
Enough "philosophy…. back to work!
You've got the footprints for the devices of the project roughly laid out for the PCB design. Spend some time now getting them as good as you can get them. It is much easier to move them now that it will be to move them later… although they can be moved later.
(I only copied a bit of the PCB design here.)
See those white lines? They are the "rat's nest", which shows you what things should be connected. They don't work like tracks, exactly, a "track" being one of the "lines of copper" which will eventually be the whole point of your PCB.
By the way: There are two cursor shapes available to you. One is a small crosshairs, the other, which you may find helpful for laying down tracks, has a vertical line and a horizontal line which extends to the edge of the drawing. You change the shape with a toggle button on the left toolbar.
Because of the nature of the process of laying tracks down, I'm going to change my style somewhat here. I will give you guidance, but won't "tell you what to do" in the same detail as before.. after I get you started.
Click on the "Add Tracks and Vias" button in the right hand side toolbar of PCBnew….
(Be sure it stays the selected button… it is easy to change the selected button to the "pointer"… by clicking the "escape" key an extra time, after using it to get out of something, for instance.)
Have a look at the "visibles" panel at the right of the screen…
For the "simple", "everyday" stuff we are doing here, what you see is fine. The critical thing is the blue triangle pointing to "B.Cu", which stands for Bottom of board, copper (chemical sign Cu) layer.
(Besides the top layer, which you will almost certainly use from time to time… once you have learned about vias… the "SilkS" ("silkscreen") layers, top and bottom, are useful. And, certainly if you are having your board manufactured by OSHPark (and also other people, I suspect), be sure to draw four lines with "Edge Cuts" to define the edge of the board. (You draw those lines with the "Add graphic line or polygon" tool, by the way.)
But! Let's lay down some tracks…
Click on one end of one of the white lines. Then move the cursor to the other end of the white line… a green line should be growing as you do this, and "rubber banding". It will acquire some weird kinks. Click on the other end of where the white line goes. That should give you a green line between the pads previously connected by a white line. The white line was guidance about what the schematic requires. If you've successfully joined the two pads, the white line will go away. Sometimes you will be very frustrated by a green line which refuses to "go down". This may be because you are trying to make a connection not called for in the schematic. Or it may be because your new line crosses over (on the same side of the board) a track you placed earlier, and to which it should not be connected. The system is trying to help you. Really!
Do click the "Save board" button from time to time. (Upper left.)
Here we see the lowest track already in place, and a start being made on the next one. Note that the pads you should connect are highlighted….
I'm afraid I must leave you to fumble about a bit getting all the tracks laid down. When there are no more white lines, you should be done.
I have a FAQ answer to "How do you lay down tracks of different widths?" for you. It isn't hard, but I would suggest that you postpone that distraction for now, if you are new to KiCad.
As long as you have the "Add tracks and vias" button of the toolbar on the right hand side of the page selected, then if you put the mouse pointer over a line and press the delete key, the line should disappear, and the white line that was there before should reappear. (Note that, with "snap to grid" in effect… which you want… you can't always get the cursor (crosshairs) exactly where you might want it… but you can move the mouse pointer to any spot. The "delete" key is looking at where the mouse pointer is to divine your wishes. If you are having trouble "hitting" something, try zooming in more.
(A brief comment on "snap to grid": I don't think you can turn it off… but you can set it to a very fine grained "grid". Bad idea. Keep it set to 25mils until you are really, really stuck… and then go back to at least 25 mils as soon as you can. I can almost guarantee that you will regret using finer grained grids until you know more.)
At some point when you have a diagonal line dragged out, but not yet "pinned" to the board, move the cursor a bit until there is a "kink" in the line, if there isn't one already, and then press the "/" key. If you don't see the effect, try it again. If all's well, the "kinking" will alternate between two possible arrangements. A mere detail… but a useful one.