Yes, your tenant name is currently [[churchcode]].focusmissions.com. To change that, you will need to open a support ticket and tell us what you would like the new name to be. Be sure the new name request is complete before you try to login or share the newly requested name. It is possible the name you seek is already in use, and we will ask for an alternate name if that is the case.
If you are looking to use your own domain, please read our support document on Custom Domains.