The traditional bowstring should have a larger loop at the top of the bow and a smaller loop at the bottom. The larger loop is meant to slide down the limb when not strung. In the picture below Karlin has the top limb resting on her foot to protect it as she puts the stringer on the bottom tip. In this picture it shows that she is checking that the bottom loop is properly in the notches. Karlin is holding her thumb on the string so the loop doesn't move out on notches as she puts the bottom pocket of the stringer over this end of the bow. Once the pocket is on the bottom tip of the bow it will hold the string in the notches.
Now Karlin holds the bow with the tips of the recurve pointing up as she puts the other end of the stringer over the top end of the bow.
With this type of stringer the rubber block goes just on the bottom side of the loop. This type of stringer works best if the bow has small tips but it needs a little more effort when stringing the bow. If the bow has long tips then a stringer with a small pocket can fit over the tip and you can still see the notches and it will be easier to string. With both stringers Karlin is leaning forward over the bow so that if anything went wrong she it protecting herself from being hit in the face by the limb. She also has her feet astride on the stringer. This adjusts the height she has to lift the bow to get the string on. When Karlin starts pulling up on the handle of the bow she slides the loop and the rubber block up the limb towards the notches. The block will only go a short ways but the closer you get it to the tip the easier it is to string the bow. Karlin will continue sliding the loop up till it is in the notches. Then she will slowly lower the bow taking the pressure off the stringer and letting the bowstring do it's job. It is important to lower the bow slowly because the string may not be in the notches properly and you see the problem and fix it without damaging the bow.
Karlin is double checking that the string is properly in the notches.
To unstring the bow the procedure is the same in reverse and easier as you can position the stringer closer to the tip of the bow.