Start slow and set goals. Meaning for example~~
week 1: run 5 minutes walk for 3 and repeat this 3 times
Week 2: increase time to maybe 10 minutes, take 3 minute walks, repeat 2 times
Week 3: 15 minute run, 3 minute walk, repeat 2 times
You can adjust this to how you progress. For example, u may want to run 5 minutes and take 3 min walk (×3) plan for 2 weeks until you build that endurance to be able to take less walking breaks and run longer.
Also remember when running (or doing other exercise) to beathe in from your nose and out from your mouth. This helps make you feel less tired and helps you push yourself to go longer more comfortably.
Also think about foot placement as you run. Proper form is what keeps you running injury free. You need to strike midfoot, not heel strike. Heel striking promotes injury and will produce shock to your knees, hips and ankles. In addition, if you decide to run, please get the proper shoes. This may sound crazy, but you cannot get good running shoes in the mall. I suggest you go to a speciality running store like "Fleet Feet", they will look at your step, gate and other body mechanics, so that you are fitted properly.
Once you start running, you may find yourself become addicted to it, so remember doing too much too quickly, is not healthy long-term. Take your time and pace yourself for a lifetime of this very exciting enjoyable sport.