running longer

New to the site....
Been running for probley 6 months. I am not very athletic at all but running to look and feel better. I run 3 miles a day but I feel like I am not doing it correctly. ?

Which is more important.... how far you run or you time? I run 3 miles in about 30 min. I know that is horrible.

Looking for some techniques to be able to run longer without stopping. Any advice??