So basically like this. in the MAINCFG you write.
This is an example.
MAINCFG CATEGORY Level Headers
Level 1
Levelname: name of level
Act: if it's a single player act 1,2, or 3 or whatever number digit.
Skynum: 1 for Greenflower zone act 1 sky
NextLevel: 2
Weather: depends what you set it to. 0,1,2 or 3
Musicslot: whatever you choose
TypeofLevel: 4096 for single player stage.