I think i need to make my Akai MPD24 the 'master keyboard' in the preferences, but for some reason the button i need to press to do so is light grey so i can't click it if you know what i mean.
I searched for it to recognise the MPD24 but it didnt find it so i added it myself and it picked it up.
I really need help using my MPD24 as a midi device because i dont have a keyboard yet.

Get back if you can. Thanks!

Have you selected the MIDI-in port in the dialog where you select the manufacturer and model?
There must be at least one entry available in that "midi in port" drop-down list. If it isn't, there must be something wrong with your installation of the mpd.