tbi rewire to fuse box,help

[BigrobDog]

i had a 90 suburban that i removed the body and put my 72 on that frame. with that motor and tranny bought a new tbi wiring harness for easy wiring . the harness i got was from ebay and was a used 5.7 harness just for the tbi .but when i got it there is a plug that goes to the fuse box, i need new fuse box, but dont know how to wire to new fuse box. is there one main power coming in to fuse box that feeds all thoes wires. not sure how a fuse box works with wiers goin in and out/. can some body tell me how to wire the wires going to fuse box