High intensity workouts... With rests in between... So for example sprint for a minute (go as hard as u can possibly go) then rest for a minute... Walk or so... Rinse and repeat... Its harder than it sounds... Remember to keep pushing yourself every day a lil bit further, and youll get there in no time =D
You need to improve your cardiovascular system. Start interval training. Go out for a jog. Pick a comfortable pace. At some point, say from one sign post to the next, sprint. Then return to a jog. Very the sprint distance & the jog distance. The goal being to raise the heart rate & then lower the heart rate multiple times during the run.
Practice makes perfect :) Train train train and eat healthy Or maybe you can go to your doctor and take a pulmonary function test to see how your lungs are working.. Then you can go from there depending on the results. Good luck and never give up