Fold downs the top two rings as in fig. 2
Fold down the middle two rings and add two more rings as in fig. 3
Add two more rings as in fig. 4
Continue steps 2 through 4 until the chain is as long as you want. Splicing the ends together is not easy but can be done by spreading the bottom end and connecting the rings.
To try something different try adding two more rings before folding down the top rings.