So I've downloaded Stockfish and the Arena GUI, but I'm having trouble getting any tablebase I download to either load into Arena, or be compatible with Stockfish. Any suggestions? I'm willing to download a different GUI if it is easy to get a tablebase loaded.
If your GUI allows custom UCI options (I think you can do it in Arena, but check its documentation), you should be able to add a syzygy path yourself. Otherwise, you may try the popular
Deep Fritz GUI. Check this link:
So Arena uses Gaviota Tablebases, so if you want to use GUI tablebase option then you can download them and configure Arena to use them,
Stockfish only uses Syzygy tablebases, So you will need those bases and then when you are configuring the engine you'll find and option for Syzygy Path. You'll need to set it to the directory where your syzygy tablebases are.