How do I get 2 Instruments to play at the same time

I was wondering how I can get a piano to do chords while a base guitar could do base I would like to combine the two I also have a question of, I play saxophone in real life so is there anyway I could use the instruments on musescore for chords and base and then I could play my saxophone for the melody. (I am brand new to musescore so is their anyway for me to do this)