1st regulate your diet. This is important if you want a genuine fitness routine you need to have the self control to ensure you are eating the right stuff.
2nd, people are right when they say cardio. but don't over do it. so many people do too much too soon and burn out. keep it steady at first. for the first month, do run twice on week, then maybe three times the second, then twice etc.
Also, id suggest initially to run for time. So go out, run 10 minutes in one direction and run back. That way you aren't getting too stuck on how far you are going, but are focusing on learning to run. as you get better you'll notice you are running further in ten minutes and that can be a big boost. ONce you are doing noticeably further, run 15 minutes in one direction then run back, and so on and so forth.
it'll come mate, just don't give up.
good luck