How do you sl2 pwise, k1?
sl2 pwise stands for slip 2 purlwise.
That means you slide your right needle into the stitch as if your were going to purl it, but don’t. Instead you just slide the stitch from your left needle to the right.
In your case, do this twice then knit the next (3rd) stitch.
What RochesterKnitter said. Slipping purlwise ony indicates how you insert the needle into the sts, you may need to leave the yarn in back to knit the next st, depending on which pattern it is.