Get clearance from your doctor.
Go to a running store and get fitted for shoes.
Buy a sports bra that has both compression and encapsulation.
Ok...now....go do Couch to 5K! The great thing about the program is that it really is designed for those who are just getting off the couch and heading out the door. When I did it in a few years, I was 240 pounds and so out of shape it was ridiculous. But I was able to do my first 5K race only 6 weeks into the program...and I ran most of it!!!
And the crazy thing about running is that once you "become a runner" it's almost like you're a runner forever, or something. I just started running again recently, after having not done it for over two years, and it only took me three practice runs to get back up to being able to run a full mile without stopping. I was really afraid I'd be all the way back to Day 1 of C25K. Nope.
About how running affects weight loss...I think that's a very individual thing. Some people lose, some people don't. It depends on how many calories you burn and a whole lot of other things. And really, weight loss is more about food than exercise. You lose weight in the kitchen, you get fit at the gym.
Hope this has helped. Good luck!
ETA: Proper running form is very important. Read
this article.