Writing with musescore, With my midi keyboard.

See https://musescore.org/en/handbook/note-input#midi-keyboard

Basically, if you want to play in real time, you will need to record into a sequencer, playing *extremely* carefully with a metronome, then save as a MIDI file and import into MuseScore. It will work about as well as trying to type a book by speaking into a microhpne and having it turned into text. Which is to say, sure, a lot of it will come out OK, but you;ll need to do a ton of cleanup afterwards to make it even close to readable.