The assistant for creating a new profile will open on first launch.

Alternatively, it can be started from the menu 'Gajim Accounts'

Select 'I already have an account I want to use'

Enter your XMPP access data:

Jabber ID = user name from the TK-Portal

Password = previously set up in TK-Portal

Click on 'next'

Click advanced in order to further customize the setup.

You can now head to settings and click on 'connections'
in order to change your server settings.

Under connections, click on 'host name'

Click activate:

Hostname = cucm-imp-1.pbx.rwth-aachen.de

Port = 5222

You can now exit the settings menu.

You can sign in on the main screen, by first changing status from signed out (1)
to available (2)