I don´t have the Gold Edition , but in another thread here, it is said that it is Civ 3vanilla and Civ3PTW with Civ3PTW as default setting. In that case you should have at least two possibilities to transfer that terrain to this scenario:
1. You can copy it as terrain folder to the art folder of that scenario (this should always work).
2.You can set in the editor the scenario search path of that scenario in the scenario/ scenario properties additionally to that terrain. At least in the Civ 3 Complete version of Civ 3 (that I use), this terrain is included in the Civ3PTW scenarios folder.
If you like Civ 3, you would be well advised to use Civ 3 Complete.
How do you start Tethurkan's scenario via gametap?
Can you play other scenarios that you have downloaded at CFC via gametap?
The editor should be here in your civ3PTW-folder (screene only temporary attached until you have seen it):