Go on itch.io to your game page, go under "more" tab, go in "admin", follow the instruction to add another person to your game.
after that also your friend can vote other game
You can already do something.
For example create your itch page of the game, with this you are able to load some test game and check if everything work correctly
before the jam end you must "link" your itch page of the game to the brackeys jam and all is done.
I already create both the itch.io game page and the repo on github with some pipeline to semplify my work
be careful to update your itch.io page on the voting period, this can ban you from Brackeys Game Jam 2025.2
dont worry too much, i play the game well, the sensivity is high but the game is still playable