How to open and close jump rings

2 pairs of pliers: chain nose and bend chain nose pliers with smooth
not serrated jaws that will not mark the surface of the jump ring.

Hold the jump ring with one pair of pliers with the opening of the jump ring at the top.

Use the second pair of pliers to open and close the ring.
The jump ring is opened and closed by twisting it, not by pulling it apart because that will distort the shape of the ring.

If you use a bend chain nose pliers to hold the ring the jaws of the pliers will not get in the way.