Simply pray at another altar. You will be asked if you either want to change prayer lists, or just want to recharge your prayer level.
For a guide on how to increase your prayer level:
http://gameolosophy.com/games/online/runescape/how-to-train-prayer-in-runescape
Chat with our AI personalities
Go back to where you changed it and tell them to change back.
No.
No.
Yes.
yes