Step 1. Taking two pairs of pliers tightly clamp each pair either side of the opening of the jump ring.
Step 2. Push one side of the jump ring away from you and the other towards you making an opening in the ring.
Step 3. Add your finding/charm/chain etc and then close the jump ring by pulling one side of the ring towards you and the other side away closing the ring. Here's a little tip for you, gently push the sides of the ring together as you do this to ensure the ring is tightly closed.
Missed the previous lessons, don't worry the links are below:
Lesson one - tools
Lesson two - findings