Can I use my own domain?

Yes, on plans that include a custom domain (see the pricing page). Your site is always available at your Felyx Photos address, and you can also point a domain you own, like book.yourstudio.com, at it.

In Settings > Domain you choose who runs your DNS, enter the domain, and add two records where you manage DNS. We check automatically every hour and set up the HTTPS certificate for you. Steps: Connect a custom domain.