Tunisian Purl Stitch is worked around the vertical bars which you created in your previous row.
I am using a different colour yarn to highlight the stitch placement.
The yarn need to be held in front of your work.
Insert the hook under the vertical bar and yoh.
Pull a loop through taking care not to catch the yarn under the hook.
You may find it helpful to hold this in place with your thumb as you work the stitch.
Repeat this to the end of the row making sure not to forget the very last stitch.
You should now have 16 loops on your hook.
Work a normal closing.
Try a few more rows for practice.