classic fast engine wiring harness help please

[esm]

ok im trying to remove and install my new fast engine wiring harness and my classic fast ---removed pass dide inner wheel well and removed old harness and see how it goes into plastic harness guide and then to driverside firewall were the fuse block is -----but my classic fast engine harness has all the ensors connectors but have no clue how to splice it in -- or do i just remove the factry harness and connector at fuse box and go from there ---i hope this makes sense