how do i make efi work on my 318?

There is as much difference between the computer carb and EFI as there is between night and day, Chev and Ford, water and dust

EFI is a complete system. "I guess" you are talking about TBI, that is "throttle body injection" which were the earlier systems, having the injectors in the throttle body.

There is going to be "several" sensors scattered around the engine connecting to the EFI system, as well as a dedicated distributor. In other words, if you cannot remove a complete working system AND HARNESS from a donor, you have a long hard expensive road.

Do you need to worry about emissions tests in your locale? If not, consider an aftermarket system like the "coming out" Holley Sniper, or the EFItech. There's a thread on them here

Otherwise, convert to a conventional carburetor and distributor. What you have is called "lean burn." There are many conversion tips on the www, google it.