I also asked this question one time, and there a guy gave me this message and now I know how to upload the game, I just copy pasted the mesage, I am surely not making any tutorial for that(I do not have time, sorry)! If other engine, you use then I will try to find something useful for uploading the game (from that particular game engine) to itch.io!
I hope you find it useful!
Regards
Roguestar