Just like when forming the knit stitch, your first step when making a purl stitch is to open or pick up the first loop on the needle, which is again in your left hand while the empty needle is in your right.
The difference this time is that the working yarn should be in front of the needle instead of behind, and instead of going into the loop from front to back, you go from back to front.
Other than that slight difference, making a purl stitch is exactly the same as making a knit stitch.
