Need Assistance does anybody else have IMac (27-inch, Late 2013)3.2 Ghz GT755M ?

I have a IMAC 27 inch 3.2 Ghz GT755M 1GB I have installed High Sierra 10.13.6 installed currently I am trying to activate my GPU to install after effects. I cannot figure this out for the life of me. What is the drivers you use and could you please direct me on what steps I might be missing. I am starting from scratch. I have been working on this for over a month. Or anybody please help. I installed a driver I can’t remember off the top of my head. I had a black screen. Then I installed a clover and read that was very bad to install Clover to install that it destroys iMac that was meant for Hackintosh I have a True iMac. Then I don’t know what to select once it says pick a series and I don’t see GT755M Graphics card and says it supports model 14,2 but don’t have a series to select? Can you help which drivers work. Thank you so much in advance I have been trying to find the answer over 30 days.