Originally Posted by
Strat
You can't use a google login for it (I have no idea why). You can use Facebook login, A PTC account login or a Niantic Kids login. What I did to use my main account (which was only linked via google account initially) was to use the legit app to link a fake Facebook account that I made to PoGo as well and then signed into PGSharp with that (keep in mind, you'll need to delete the original 'legit' app to use PGSharp too). Pretty simple to get started up and running. If you need any further help, just let me know.
Also, if you regularly buy coins in the in-game store, you'll need to use the legit app to do so, PGSharp obviously will not support this.