Wizard101 advice on decrypting packets?

So I'm trying to make a server emulator for a game called Wizard101, and I'm experienced in networking in Python which is what I plan to make the server in, but using wireshark I have no clue how to start on decrypting packets. Some are obvious, like when you get to character select screen, it sends you stuff as "WizardZone_TheCommons" because one of your characters are currently in a zone called "The Commons". But almost everything else is encrypted, and I don't want anyone to give me a step by step guide or anything, but how do I start on decrypting packets?