Go to: https://www.chess.com/analysis
Click "Load FEN" and paste "8/6Kn/1Q4B1/3pk3/8/8/5P2/8 w - - 0 1"
It will then show you various different lines one of which is a mate in 3.
If you only want a hint the first move is to do with the queen.
Qc6 <--- highlight here for the move if you are still stuck
White to play and win in 3. I've been looking at this for days and getting nowhere!