SubFire 2 players have 2 primary ways to enter the credentials to log in to your server.
The first is the standard Credentials dialog, which is the same on all applications. This gives you the page to name the server, give its URL, and enter your username and password. Multiple servers can be configured. Once added, servers appear on the front page of most apps (in some apps, almost every browsing page) so you can switch between them quickly.
To delete an entry (like the Demo instance), it has to not be the one you are currently logged in to. Connect to a server you are keeping, then go to the Credentials page. Select the server you want to delete and press the Delete button.
The second means works when you have already logged in to a SubFire 2 mobile or desktop client (M2, Dash, Base, Timer). On the new client, click the "Link Client", and you will see a 7 digit number. Then on the supporting app already logged in, click the "Link Source". enter the same 7 digits and all of the logins on the Source will transfer over to the new Client, which will then log in to the selected server from the Source.
You can also connect with a special Link app for just this purpose, http://subfiresuite.com/link/ or https://subfiresuite.com/link/. The protocol matters: which ever protocol (secure https or regular http) you use for your apps has to be used for the link app to find the current credentials to exchange. The credentials are encrypted on exchange through the SubFireSuite server.
For the upcoming upgrade of SubFire 2 for Amazon's Fire platform, there will be a screen that can import your previous SubFire 1 credentials. On the TV version, it will come up on the first startup. For Mobile, you will need to enter the Credentials screen and click the Import button.