Pictures of wiring please

You are going to have to give us a bit 'o detail. What engine do you have, for starters?

Much of this "only fits one way." Certain "key connectors" only fit one place. Example, look for the end of a harness with a large ring terminal. It either goes on the starter or the alternator, depending on the size, or the starter relay.

Other wires you can ID by stuff like the color. Oil sender, temp sender, etc. are wires which break out singly with a single connector.