White’s knight is on a dark square. So are Black’s king, queen, and rook. Ne6+ would be great, but White’s queen is in the way. The question, now familiar, is whether the queen can make a move that will force a response from Black that costs him a move. You might start by examining, if briefly, any checks the queen can administer, but all of them cause either Black’s king or queen to move, ruining the fork. So now look for captures the queen can make without giving check. There is just one: QxN. What follows from that? Either g6xQ or RxQ; and either way, Ne6+ picks up Black’s queen and wins a knight with the sequence.

Incidentally, it may come as a small surprise to you to hear that White's rook on c1 is doing absolutely essential work in this position. Do you see why? It protects f1. If the rook on c1 were gone and f1 thus were unprotected, Black would reply to QxN with RxQ, aiming his rook at White’s back rank—and then after White finishes his knight fork with NxQ, Black has Rf1#, checkmating White’s trapped king. The moral: be ever mindful of your own king’s vulnerabilities and how any offensive sequences you are planning may unexpectedly expose it to checks (and worse) that are not possible on the board in front of you.