where do i put them in the game files to use them?

if you use 1.27 you can use the save file manager that comes with it

C:\Users*username*\Documents\Rockstar Games\GTA V\Profiles

But I would really recommend Installing Patch 1.27, Link is here: https://github.com/TwosHusbandS/Project-127/raw/master/Installer/Project_127_Installer_Latest.exe

You can play upgraded and Downgraded with that, has many features and whatever is done, you will enjoy using it!