switching clefs, treble to bass

I would like to start a library of quality music themes and older melodies that are not available anymore. I have used the musescore to write a Brahms theme. I can figure out how to transpose key signature and pitch in the treble clef, but also would like to be able to take the score, and put it into bass clef for low brass, and transpose for cello and bass. Or do I need to enter a bass clef version of the music, along with a treble clef version. Thank you for any assistance.