To avoid conflict, you need to make sure you opened the correct roblox process (high memory usage) and not the secondary one only used for roblox's AC (only uses 10mb of RAM).
Once you've closed the background roblox process (OR opened the correct process in cheat engine), go to Memory View --> Tools --> Lua Engine --> Ctrl+V the script in the text box, and hit Execute.
3/21/22 - Fixed a bug
After a long duration of side projects, I've come back to redo this completely.
In order to run scripts using nothing other than Cheat Engine's own Lua Engine, you only have to run 1 script -- executor.lua
Go into Memory View and hit Ctrl+L or Tools --> Lua Engine and paste the script there.
Make any changes you want to the FE Fly script which is in a large string, in the first couple of lines in executor.lua. Replace it with any script you want. Just nothing crazy cause I've never had a chance to finish this thing.
DONT use 'Open Cheat Table' for executing the lua script
That is all. :)