Text above join page boxes

I'd like to get some text above the 'General Info' header on the join page. Can't see a way to do it through the dashboard. How do I go about getting it up there? Apologies if this is very basic stuff - I'm at the very bottom of a very steep learning curve atm! Thanks PT

I am also interesting on this one..

Where should i add a table for example? where in join.php?

thank you in advance