Do you have a WAD file containing Quake's textures? If not, there should be a program named "MakeTex" in Worldcraft's folder. When you have the WAD file with the textures, go to Worldcraft's configuration window (from menu File->Configuration, iirc), find the tab where the WAD file should be set, click on the button to browse for the WAD file and add it to the list, and you're done.
Set Worldcraft's 3D view to "Textured mode". If the textures were correctly loaded, they will show up in there.
And the texture browser displays all available textures from the WAD file.
I don't know if the process is the same in the newer version of Worldcraft, but the manual/help file can help with that.
After setting the configuration correctly, open the map and select all brushes from the teleporter together. Right-click on the selection, and click on "Move to group" in the context menu. All of the teleporter's brushes will be "glued" together as if they were a single object. Make sure it's still selected, and copy it with Ctrl+C.
Go to the menu File->New, select "Quake" as the map type, and paste the object with Ctrl+V. Move it to the position '0 0 0' inside the editor, add a couple light entities around it, save the file with a new name, and build it.
Ph'nglui mglw'nafh mankrip Hell's end wgah'nagl fhtagn.