What happens after you confirm
The review site is built in the background. You do not need to keep the registration page open. Use Refresh status if you come back to check progress.
Keep the private return link to this registration. Do not share it.
When the site is ready, an administrator looks at it. They may approve it or ask for a change. Your group is not invited until it is approved. After approval, the committee email receives a link to the new site and a link to set a password.
Your current website stays as it is while this happens. The group decides later whether to continue with the new site.