New to diet and fitness!!!

Hello everyone!

I'm new to this world of diet and fitness, so I've got  a million questions.

First of all, I would like to tell you about myself first.

I'm 28, mother of three, just had my baby girl 3 months ago.  I've always been very thin.  I'm about 5'6" and 100 lbs on a good day, but I can safley say that I haven't been in shape scince grade 8.  So I recently bought the yearly gym membership, and now go about 3 times a week, for 2 weeks now, maybe 3.

A few questions I have are how do I lift weights to add muscle mass.  My arms are paper thin, and I would like to bulk up. 

Also, are there certain exercises that I can do to build up my rear? Being thin, I've never had a butt, and thought that it would be nice to finally get one.

I would also like to be able to increase my jogging time on the treadmill, any advice on how to push myself to be able to jogg the whole 10mins instead of 2 here and 4 there?

I also started counting my carbs and proteins and calories, so that I know that I am getting enough, and advice on how to do this properly?

I've been searching the internet, but everything is all so overwhelming!

Thankyou for all your help and advice!