How to Improve Walking Endurance
Walking regularly, whatever the speed, is good for the mind, body and soul. It's free, simple, and adaptable to your schedule. You just have to keep at it! If you try to walk a little further every day, you'll find that your walking endurance gradually improves.

Walk for at least 30 minutes 3 to 5 days a week. Going for regular walks improves your cardiovascular fitness gradually, but don't sweat it if you can't walk this long initially. Over time, your body will get used to a certain level of activity, and that makes it easier for you to walk longer.
Go on a longer walk at least one day a week. Plan a longer walk for at least one of your sessions so you can gradually push your endurance. When you first start, the distance will likely be relatively short. However, as you progress, the distance will grow.
Walk at a brisk pace of about 3 miles (4.8 km) per hour. This pace is faster than a stroll, but likely not the fastest you can walk.
Walking on grass or sand is more difficult than walking on a paved walking trail. Including plenty of hills on your route helps build your stamina as well.
Carry weight while walking. If you only have a short period of time to walk, add resistance to work on your stamina. You can buy ankle and wrist weights at sporting goods but this type of equipment isn't strictly necessary.
Think of what you do throughout the day and figure out how you can introduce more walking into the mix. You'll gradually build stamina by getting your body accustomed to moving constantly rather than being sedentary.
Because bodyweight exercises don't require any equipment, you can do them anywhere. Any downtime you have waiting for something or someone can be put to use to help you become more active, even if it's simply doing a few jumping jacks or toe touches.