This board is for people who have questions or need support about itch.io. We can’t really offer you advice on how to build a game, as there are hundreds of tools available. I recommend doing a search online to see what you can use.

I may be wrong, but I suspect that the OP thinks that itch.io is an online game maker tool in itself. 

Just answering briefly to the OP considering the above, itch.io is, in very few words, a publishing platform for your creations, considering they're game related (games, tools, assets. resources, etc).

The next thing, if this is your first try on game making, as 'dulsi' recommended, we may help you better if you answer a little bit more about your knowledge in this subject. 

Hopefully, this answer may help you a bit.

Cheers!