Edit drum set to include more orchestra percussion?

I recently discovered that when you click on a percussion stave and bring up the piano keyboard, when you play each note of the piano it corresponds to certain percussion sounds that I previously didn't know existed until now. I can't figure out how to edit the Drumset to include these sounds. I know certain percussion sounds are there already in the files of Musescore, such as the Guiro, but I just don't know how to access them on a percussion stave. Any ideas?