On a PC (the not Steam version and they go in the folder shown in the screenshot. I don't have a Mac, but I'm sure there is a jersey folder in there somewhere.
If you manually load files, you can organize them in subfolders so they are easier to find. The GOAT folder you see is just that. One you click it, I have the two leagues and then each team with all of that's team's jerseys in their respective folder. I just leave the default ones outside the folder. but organize it how you like. A jersey may have to NOT be in a subfolder for an auto-naming convention to work and auto-load it....
but anyway, that's where they go...
