What tutorial are you following as you do not provide any link to it.
Please look at all tutorials here for Wix Bookings and you can open them all in your own Wix Editor and see the pages all setup with all code provided too.
https://www.wix.com/corvid/examples?category=bookings
You can see more info about the Wix Bookings collections here.
https://support.wix.com/en/corvid-by-wix/wix-bookings-with-corvid