In Sibelius, to input music onto the screen (& make printable scores) all you need is an electronic keyboard with Midi In and Midi Out sockets, plus a Midi cable. You play the notes and they appear in the score, sort of like a musical word-processor, and you can then get the programme to play everything back to you. I know there are other ways of doing it but this is the method I use, which works for me.

Bear in mind that you can only do one staff at a time (though you can do chords in each), so if you want both bass and treble clef (as in piano or harp music) you need to input them separately, though both staves will play back simultaneously. Our music school has both Sibelius and Finale, but Sibelius seems to be the favourite among the staff.