If you in test flight we still have 58 days of 1.5(4) which works fine for zapping. So no rush in getting altstore set up.

I recommend going though the altstore process and set up their Nintendo emulator first, nice added bonus to play some roms on iPhone. Once you got that process down, there are a couple of things you gotta set up for sideloading in general like the mail plug-in & dev mode as mentioned above, then adding sideus should be simple.