After you imported it into the OE, did you build it and copy the .shp and any .htx files into your userlib folder?
Re-open the OE, it should always be there on the second open after you build it (edit) and copy it into the userlib folder.
Later, start a test terrain, everyone has at least one, if not a folder full of them hehe.
Edit: All this OE stuff subject to change after the update.
Oh, and you'll find the new shape in the newshps folder, just in case you're wondering.