I was quite unsporty for many years, until I started to like running about 3 years ago. When I began I could just do a short distance, always walk, run short thime, then walk again and so on. In autumn last year I reached my goal and took part in (and finished) a half-marathon 
With every sports it’s important to start slowly to not overstrain your body, but it will adjust soon.
Additionally, since I started a new job where we can visit a gym for free, I’m going there 2 times a week, which is a very good addition to running and also helps my bad back a lot.