I've cast-on 10 stitches.
Put the tip of the right needle from back to front of the first stitch on the left needle.
Pull the working yarn ro the front.
Wrap it counterclockwise around the right needle and
Pull it through the stitch on the left needle and this will put the right needle on top of the left needle with the new stitch on it.
Slip the stitch off of the left needle and onto the right needle. You've made your first purl stitch!
This is one row of purl stitches.
10 rows of purl stitches.