Completing the mate in the same coloured corner as your bishop.
This is probably the easiest part of the mating pattern (with achieving the first position shown of step 2 the most difficult)
So step 3 starts off with this position.
The black king is left with 2 options, Kh1 or Kh2. Either way it is doomed.
1…Kh1 2. Kg3 Kg1 3. Nf4 Kh1 4. Bc4 (move needed to avoid stalemate) Kg1 5. Nh3+ Kh1 Kd5++
Kh2 is treated quite similarly, which I'll leave as an excercise. The basic aim for white is for your bishop to block 1 escape route, while using a combination of your knight and King to block the other. You need to use the knight to check the king back into the corner, and then deliver mate with the bishop.
And I think that is that. I'm willing to play a few games as the lone king to help people who want to play through the tutorial (thanks to Schakuhr doing this for me a while ago), so pm me or send the setup game, if you wish.