How do you improve endurance?

By training and pusing to yourself to do more each time. For example, you want to learn to jog, but can only do it for 2 min before you feel you need to stop; then slow down and walk for 1-2 min and jog again on off or 30 min. The next time you go out to run (I'd say every other day), you should try to run a littler longer, say 3 min before slowing down. If you keep increasing the interval, overtime you should be able to run the whole 30 min non stop.