Click on Submit and a prompt will open in order to select (or create) the page for your game/translation. That's it.
Format wise, if you leave the game in its original HTML format, visitors can see it directly online, without needing to download it.
That's what I would do: after all, translating HTML can be as simple as opening the index.html file with notepad and overwriting anything outside "<>"
But itch accepts any kind of format. You're skilled in design and want to send a PDF? Go for it. Want to keep it simple and send a .doc file from MS Word? No problem. You're a master with crayons and want handcraft everything on paper? Great, scan and post it on your page.
I might end up repeating myself but if you A) refrain from nudity or hateful language or visuals and B) respect the CC license of the game (attribution, non commercial), you are free to do anything you want.
Make it yours and make it cool!