Wiring is probably the most challenging aspect of a motor swap. Depending upon the differences in the target car and donor engine. of course - some combinations require more work than others.
I put a JDM OBD1 engine into a USDM OBD0 ride and took the wiring/ECU up to OBD1. Distributor wiring had to change, O2 sensor went from single wire to 4 wire, engine EAC/IACcontrol solonoids, and the ECU connectors.
For me, I used schematics. Had to troubleshoot it to get it to run. I tried the "blue wire to yellow wire" from online forums and it didn't get me there. The schematics were great not only for the initial work, but for the troubleshooting. This could just be me and I'm ok with that - but, I like maps too when finding a location. I don't to well with verbal directions like "take the third right turn, drive 3 blocks past the tree stump, hang a slight left and it's on the right".
I suggest you get a good set of wiring schematics for your car and also a set from the donor car (year and model) the engine came from.
Schematics will allow you to ring out the harness's pin to pin from the ECU to the engine and if you go into the troubleshooting mode, that's very likely going to be necessary.
Good luck with your project - Welcome to the HS Forums!