Each store asks for the same facts in its own order and words: title, author, description, categories, price and files. The kit lists them for each store, filled from this edition, with the store's own limits checked and the files to upload.
Choose a store above the kit. The studio shows only stores that sell this edition's formats in its language. It never uploads to any of them: you sign in to each store and publish yourself.
Going through a distributor? A distributor such as Draft2Digital or PublishDrive delivers your book to many stores at once. Don't also upload to a store directly if the distributor already sends it there: readers would see the book twice. The guide to publishing wide says what each store and distributor pays.