Time capsule access over internet, static ip

Hey guys,

I've been trying to get this to work for a few days now, and can't get a solution that's both permanent and will allow me to send to friends/ colleagues.

I want to access my TimeCapsule over the internet to get at my files. I have it connected to a Linksys DIR-615 router and the router to a modem.

If someone could explain how to set up my airport utility, and the ports for the router, I would be happy. Explaining how to make my time capsule have a consistent IP that i could redirect my domain's DNS to would be amazing.

Thanks in advance!