If you go to the administration page, does your External Accessibility Check pass? If not, you should get that passing first. That would put you at Step 4 of our Getting Started Guide:
http://help.screenconnec...ettingStartedGuide.ashx

Once your installation is externally accessible, you can figure out how you want to address it. Do you know if you have a static IP address? If so, getting a domain name (such as "example.com") and pointing it to that IP is pretty straightforward. If not, it gets a little more tricky.