Your "kit" is missing some pieces. You'll need
- a non-contact voltage tester (voltmeter or non-contact tester will suffice).
- A 5-pack of colored electrical tape.
- 3-void Wago "Lever-nuts" - like these, but they latch down with a lever, and allow reuse.
- 3 feet of black THHN wire, solid not stranded, and 12 AWG wire size. (even if your breaker is 15A, #12 is the universal donor).
- 1 foot of bare, solid #12 ground wire.
Prepping the wires
Unfortunately, "#1 #2 #3 #4" is not standard nomenclature, if anything the builder can be guilty of "stating the obvious". Unless you open up the 3 light fixtures and find "oh look, the other end of this cable is also marked #3, and that other light is #2". shrug
So we'll need to test which cable is the supply.
Turn the breaker on, and tap each black wire with a non-contact tester. One of them should light up.
Mark the other 3 black wires with red, blue and yellow tape, respectively.
If you want to know which wire goes to which light (for arranging the switches to your preference), let's not do that now.
The problem with those "push" connectors is you can't insert a wire, pull it out, and reuse the void a second time. Pulling the wire out destroys the spring clamping force in that void: it won't clamp properly, will arc and start a fire. So if you need to do any experimenting at all, rend (pull/twist) the wires out of these nuts, and use Wago lever-nuts. Don't waste wire length and why bother re-stripping?
Prepare the pigtails
Cut your 3' wire into six 6" pigtails, and strip off about 5/8" of wire off one end. (off the other end, strip off whatever the connector says to on its labeling).
Take 3 of your pigtails and the colored tape. Wrap one pigtail with red tape, another with blue tape, and another with yellow tape.
Cut your 1' ground wire into two 6" pigtails.
Prepare the switches
On a nice comfortable bench, sit down with the 2 switches. Use the screw terminals and do proper shepherd's crook screw connections, clockwise. Skill up on Youtube on those. Alternately you can get a slightly better switch that uses "screw-and-clamp" connections, a back-wire where you tighten the screw (HARD) to clamp it.
"Why not just use backstabs"? They are known unreliable, and anyway don't work on #12 wire.
"Why not just use #14 wire?" That would be bad if the breaker was 20A.
The single switch is easy. Pick any screw and put a black pigtail there. The other screw gets a red pigtail.
The dual switch is tricky, because you must look closely for which side is "common". It will have 2 screws on "common" and a little metal tab that could be broken off to separate the two "common" screws. Do not break the tab. Put 1 black wire on "common" and do not use the other "common" screw.
The other two (non-common) screws on the dual switch get a blue and yellow pigtail.
Both switches get 1 ground pigtail on their green screw.
Feel free to wrap the switch bodies with electrical tape 2-3 times around, to insulate the side screws. However, hold off on that until the switch positions are where you like.
Back to the switch box
Breaker still off.
Super easy. Bare to bare. Black to black. Blue to blue. You're getting the idea.
See how all the prep work above made this Super Easy? That's why it's worth it.
"But I don't like which switch controls which light". OK, turn off the breaker and exchange wires on the screw terminals (or screw-and-clamp's) as needed. That way the pigtail colors stay matched up.
