It's easiest to use needlenose pliers or similar tool.
Gently squeeze or stretch links, alternating from one side to the other, all along the ring band.
Test ring size, then adjust more if necessary.
An easy way to enlarge ring evenly is to insert one tip
of the needlenose pliers
in between the links as shown below,
then close the pliers.
The farther in the pliers, the more the ring will be loosened.
Do this alternating from one side to the other as above.
The ring can also be sized with your bare hands.
It's not as easy, but I have done many that way!
If you have any comments or questions regarding these instructions,
please let me know.