How to update mobile substrate when it is available?

I'm waiting for the mobile substrate update for iOS 7 jailbreak. How will I be able to update the mobile substrate? Via cydia? Or will I have to re-jailbreak my iphone?

Do a search on Cydia for Mobile Substrate

Mobile Substrate should've been installed already in Cydia. If not, do a search for it and it should show up. Make sure you check the box next to it.