Welcome deary, I am a newbie myself. I've been battling my weight since I was little and then in my teens it evened out and I was about 150 and then I had my son and well, last time I was at the doctor's I weighed 238, darn near 100 pounds
Anyways, healthy eating is good for every member of the household, fat or thin. Not only do we have to watch the weight, but high cholestoral and diabetis don't care if you are fat or thin, so we need to eat healthy for those reasons too. My husband has a hard time realizing that,
As for you not knowing what weight range, I am almost 5'5", so I am a little taller than you, but weight range isn't just age and height, it's also body build. I'm bigger boned, so my lowest should never be less than 135. I'd go to the doctor and find out exactly what range he/she would like you to be in and shoot for that weight range.
Welcome and goodluck. This site is great for support and I hope that you find it as wonderful as I have