I am not an electrician so this is only the way I wired my main service. There might be faster or different orders to do this so pick and choose from the whole site. What you need for your build. I am also posting this as a member and should NOT be considered as advice from the boards administration.
This is an ongoing work so I will edit as I get the pictures in order. If you see something that needs help or have a better picture please PM me and I will be glad to edit.
120 vac. The circuit beaker
This is a 30 amp, 2 pole, 120/240vac load center. It allows two circuit beakers that are 15 amps each. Purchased separately.
This needed a ground bar purchased separately, You can attach the ground bar before or after you wire it.
Next take your incoming Romex or stranded wire. 12-2 or 14-2 with ground. That will give you a white (neutral) a bare (ground, might be green also) and a black (hot) wire. Strip back the wire enough to give you about 4-6 inches of separated, but still insulated wires. You will cut off what you don't need and leave some play.
Next knock out the plug where you want your wires to go. Mine is on top. Add a squeeze type Romex connector to the wire and put the wire through the hole.
Wire the ground first. (See copper wire above) Stick it through under the screw and tighten the screw. Then I put the squeeze connector in the hole ( get a couple from an electrician. You will only need 3 to do what I did)
Now, take a piece of black wire a few inches long (what will fit your space) strip about 3/4' off and make a jumper.
Put the jumper from one of the top screws to the other and strip off 1/2" of the insulation from the incoming hot (black wire) and add it to the first screw and tighten down. Tighten down the second screw with the jumper only connected. This makes the second breaker hot.
Take the white (neutral) wire to the top neutral bar, strip it back and screw it down. That is your incoming. On to the outgoing!
This shows the outgoing ground. You will make a similar knock outs for the outgoing wires. I used two. Strip the wires, and add the connectors.
Wire the outgoing bare ground wire the same as the incoming.
Wire the white (neutral) wire to the bottom neutral bar. See above.
Wire the beaker. Do not unscrew this screw..........loosen it only. Strip the black wire and stab in your wire. Tighten the screw. You will do this for both breakers. Adding a bare (ground) a white (neutral) and a black (hot) for each breaker. Remove the white arrow sticky strips if you have them. Push the breaker into the slot and make sure it clicks in. TURN TO OFF and leave it there. Do the same with the second breaker.
Wired out going
Wired load center. Tuck in all your excess sticking out wire.
Remember to turn the switches to OFF AND LEAVE THEM THERE until everything is hooked up.