There is a path from Styhead Tarn near the stretcher box that leads to the Napes. If I remember correctly some cairns show the way toward Kern Knotts. We had to climb up a gully to get to the base of the Needle after traversing around the fellside. This was when we climbed Needle Ridge with Midweekmountain as guide a few years ago. I've never threaded the Needle so I can't offer any advice on which is the best way to do it.