Are you on the heel flap? In the patterns I've used the first stitch is often slipped to make the sides easier to pick up later.
Anywho, slipping a stitch means to just slide the stitch over without working it. If it says knitwise, slip the right needle into the stitch as if you were about to knit and slide it to the right needle. For purlwise, just insert as if to purl and slip.
Hope this helps.