Absolutely! Singlepage is designed to work with clients' domain names.
You can either use a domain name you have already registered, or you can register a new one with any reputable domain name registrar. Singlepage does not offer domain name registration as a service - there are already so many registrars offering a good service at low prices.
Registering domain names is easy and inexpensive - for example a .co.uk name should cost just a few pounds a year to register and renew.