How to Help Tanks in Dungeons 101.

[Arriverderci]

From what I can find on the internet, you hit square with your target highlighted, and it'll bring up an option to mark the targets. From there, it'll give you a list of available marks. The marks can be put in a hotbar to quickly mark targets.

Thank you friend.
I was scared to try tanking on PS3 but maybe it won't be so bad now.