Slip stitch question

How do I slip 1 st firmly with yarn at WSF.
It asks me to knit to last 5 stitches, turn, then slip 1 st firmly with yarn at WSF, then next row I purl to last 5 stitches, turn, slip 1 st firmly with yarn at WSF. Help please.

Welcome to the forum!

Your pattern probably defines WSF, maybe Wrong Side Facing? It seems as though you’re always slipping with the yarn on the wrong side (the purl side).
Can you give us a pattern name and a link please?

You just do what it tells you. Turn when you have 5 sts left, bringing the yarn to the WS and slip the first stitch.