I'm a newbie too
Measurements are a pain in the butt... I'm not totally sure, but when I looked online I always found directions to measure the largest part of the bust, the largest part of the hips, and the smallest part of the waist, about 1-2 inches above your belly button. That seems to be the consensus on sites talking about clothing measurements, at least. At any rate, since the change is what's really important, I guess if you're consistent it doesn't matter TOO terribly much where exactly you measure. Welcome!