Sorry if my English is bad, but i speak spanish
it is my first time using itch,io
And i don´t know much about buy games here, in this page i buy the game, and then where can i find the game to install? and what about updates?
When you purchase the game, it is added to your library and a banner is displayed on the game's page indicating the purchase.
As for updates, you'll have to update them manually by going to the page and checking if there are any new features, although I think it's unlikely that there will be since the game is already complete.