Preview https://youtu.be/Cca2ikE-aBo
put the jar and json file in a folder named: GamerclientV1.2 put the folder in %appdata%/.minecraft/versions goto the minecraft launcher select installations then new and selcect by version GamerclientV1.2 and then just selct GamerclientV1.2 under the tab play and press the play button enjoy.
Pringle.ccp for inf jump