I would start with playing some basic chords and such. Just so your muscles get used to playing again. Try to play at least 5 mins a day, because your muscles have memory and they store certain movements. It is better to play 5 mins a day then not play for 3 days and then play for 3 hours the next day or whatever. After you are done with basic chords move onto some scales and try to refresh your memory. Then learn everything you already knew before hand if you want or start learning something new. The main goal is to play SOMETHING for 5 mins a day, to build muscle memory.