Transposing up the fretboard

I wrote out a song in Musescore, in bass tab - in A, so it begins on the 5th fret of the E string. I need to transpose it to C for our singer, so I want to transpose it to C. If I use the transpose function in Musescore (and I've tried it a number of different ways) it seems determined to begin the score on the 3rd fret of the A string. I want all of the whole song to move up three frets so it begins on the 8th fret of the E string with all the other notes simply also moving up the same strings three frets on the fretboard. Does anyone know how to do this?