Tenor Drums

Do you mean, you are looking for the sound of a tenor drum in playback? That should just be a matter of finding a Soundfont somewhere online that includes a sample of that type of drum. The Soundfont included with MuseScore includes only the sounds defined by GeneralMIDI. But the various tom sounds should be all but indistinguishable from a true tenor drum. So if you create a staff using one of the toms, then just change the name of the staff, you pretty much have your tenor drum.

If you're regularly doing drumline sorts of things, you might want to do a search and find the other threads where people have posted their own template and so forth with these things already configured; I believe there have been soundfonts posted as well.