Your 4-wheeler's tires take a thrashing, it's just the nature of the sport, but when your tire comes off the rim or starts losing air while you're on a ride, you need to know how to properly seat your 4-wheeler tire so you don't get stranded out on the trail.
Since 4-wheeler tires have the potential to come unseated, you should be prepared by bringing some common tools with you. For this job you need: A small air compressor that has a quick release hose attachment. A webbed tie-down clamp and needle nose pliers.
To seat your 4-wheeler tire again you will need to take the rim completely off. You can try simply tilting your 4-wheeler if you have some help, but trails are notoriously uneven and if your 4-wheeler gives way, you could be seriously hurt. Better to take off the rim and play it safe, it will take a little longer but it's the safest way to do it.
Now using your webbed tie-down, wrap it all the way around the 4-wheeler tire and crimp it nice and tight. Next, remove the inside tire valve with needle nose pliers. Remember, "Righty-tighty" so turn to the left and your inside the tire valve. Using your air compressor, fill the tire with the quick release hose, and if you notice air is leaking anywhere around the rim, try tightening the crimp a little more.
Once you have the 4-wheeler tire properly seated again and no air seems to be leaking, quickly screw the valve back (righty-tighty) on the tire, and continue filling the 4-wheeler tire to the manufacturer recommended PSI; then you'll be back on the trail!