Sometimes you won't find the answers you need on GreekChat or any website for that matter. They can, however, point you in the right direction.

There's a process your sorority needs to follow if you ladies want to affiliate with a(n) inter/national organization. The link I posted above will take you to the NPC website if it's an NPC organization you're interested in. If it's a service organization, I'd contact their HQ.