Nothing. For some reason, some people (including me) are unable to access the help file by clicking help. Try looking in C:/Games/Jazz2/JCSHelp. You may be able to find instructions there. If not, you could also look online. J2O has some links to good JCS help sites.

Regarding the tileset, you must save a compatible picture (.bmp .anm or .pcx) in the C;/Games/Jazz2/Tiles folder in order for JCS to find it, and include it in the drop down menu.