Configuring a Grandstream HT503 Device to act as an FXO Gateway

General Help
1

So I got me one of those HT503s. Now I am going on this article as listed in the title of this topic.

Configuring a Grandstream HT503 Device to act as an FXO Gateway (and the whys behind setting up an FXO appliance)

Step 1 was a success. but I am already stuck on step 2.

Step 2 assumes you have the device on the same LAN as the PBX. What does one do when they are not?