Black ops 1 saved file wont drag into horizon

I am trying to get a call of duty black ops 1 mod with horizon and my file wont drag into it

Is it a .gpd file?

GPD or Basic Save Game ? IF it’s a GPD simple open your profile and replace the GPD in your profile with the one you have to use it and if it’s a save you should be able to just open it in horizon the GPD thing sound more what you’re doing