Good evening to all,
I have created a small circuit to power 6 leds with a serial resistor (one layer).
This resistor and the two power supply wires will be soldered directly on the bottom of the board, at the places indicated by the arrows.
These areas must therefore be conductive.
How should do so that they are not covered with varnish?
Thank you in advance for your advice.
Pascal
If your PCB as a resistor, then put the resistor in the schematic and assign a suitable footprint to it.
Same for your connector pads. Draw them in the schematic and add footprints. The simplest footprints you can make are SMT footprints with a single pad.
KiCad has a quite capable editor for making custom footprints. The first few times there will be a bit of a learning curve, mostly because you also have to learn some library management.
Once you have learned how to do it, you can make such simple footprints in a few minutes.
Also:
If you want to solder flexible wires to your PCB, then these break very easily right at the spot where the solder ends in your wire, because they get bent repeatedly in a small area.
Drilling a hole in your PCB some 10_mm away from the SMT pads and putting the wire though that hole helps a lot to prevent this. Also gluing the wire to the PCB or fixating it with some other method such as tie-raps is an option.
There are solderwirepads in the standard footprint library, including a couple of SMD ones. If those don’t suit you you can modify them for your custom pad.
With KiCad you work at the level of components: symbols and footprints, which then insert all the associated artifacts (pads, holes, mask, etc) onto the PCB, rather than you putting those artifacts by themselves on the PCB.
Do you need a second pad for the resistor?
As @paulvdh and @retiredfeline suggest, use a resistor footprint, but if you wish, edit the footprint pads (double left click) by changing the X & Y & shape. You can also edit the hole size to “0” so there is no hole. Kicad will complain briefly that the pad has no hole but just ignore the program. 
Same with the connectors, edit the pads to suit and hole size to “0”.
Hello,
The simpler (for me), the better…
So I tried the method recommended by jmk, and it seems to work perfectly.
However, when you look at the 3D view (from below), the pads are grey and not yellow like the others. Is this normal?
Pascal
I don’t know.
True confession time… I have never bothered with 3D 
Gray pads are covered in solder paste (F.Paste layer in PCB editor) as it is the default for any SMD pads. If you won’t use stencil solder paste application (like it is used in mass maufacturing) you can safely ignore it.
If you don’t want to se the solder paste in 3D viewer, just uncheck “Show solder paste layers” option in 3D viewer preferences.
Doing that is really not much simpler then creating a custom footprint.
The only added “complexity” is the library management, which is about a handful of mouse clicks and typing in the name of the library.
And in the long run, that method will be simpler, because it keeps stuff together if you have to make a revision of your PCB, and you can also re-use the footprints you made in other projects.
Also:
rotate the two bottom LED’s, to put all LED’s in the same direction. This does not matter for the PCB itself, but it is a lot easier during assembly.
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