Where do I buy a domain?

You buy a domain from any registrar — Sellit doesn't sell domains. For a .ge domain use proservice.ge or domain.ge; for .com/.store use Namecheap or Hostinger. It usually costs a few lari a year. Once you own it, come back to Sellit → Settings → Domain and connect it. Before buying, the "Check" button on the Sellit screen tells you whether a domain is free or taken.