Purl stitch is very similar to the knit stitch, except it is done backwards. So instead of having the yarn hooked on the index finger it is pooled by the thumb all at the front (see the right position on the left).
Slip the stitch off the same way as before knitting.
To make a purl stitch push the needle trough the loop from behind, wrap around with the yarn (use the thumb to do this) and pull back through with the loop on the left hand needle.
And this is it, you know the basics!
Rasa xo