Linen stitch

My pattern reads: WS: P1, YB, S11, YF I understand what the abbreviations mean just don’t know how to do YB or YF. Please help

That’s just a term for move the yarn to the front (yf) or move it to the back (yb); just like you move it when switching from knits to purls. This - S11- is really Sl 1, slip 1 stitch as if to purl with the yarn in back.

Linen stitch can also be written this way:

Row 1: K1, sl1 wyif - repeat to end
Row 2: P1, sl1 wyib - repeat to end