UMSWE and the TFT editor are not the same. Do you have UMSWE for TFT or for ROC?
If you have TFT...
Open the import manager by clicking on its icon near the top, by the Object editor and whatnot. Clcik the import button and select your file. If there is a texture (.BLP) associated with this, import it too. The path for the BLP should be specified in a Readme; change it to the path by double clicking on the BLP's line. You have to restart the editor before any new models will show up.