XML with Flash-loading text

I’m new to XML and i’ve read the tutorials on this site, they’ve been helpful but I can’t exactly figure out the thing I need to do:

I’m making a site in flash for a client who will want to update her own text (without going into the flash file). This is what I’m having trouble understanding:

a) How do I have the text show up when a particular button is pushed? For example:
When “about” is pushed, the about text “loads”, when “contact” is pushed, the contact text “loads”.

b)is there a way for URL links to be on any of that text that was brought in?