Your flat tire is actually a good omen. It Hookless mtb rims means that you ride often enough to have finally done damage to your two wheeled vehicle and you are being rewarded by learning to fix your trusty bike. Good job and keep it up.
If you are fixing your tire at home (as opposed to out on the road), prop your bike up on your bike repair stand if you have one. If you are on the road, make sure you are completely off the road and in a safe location. Before you take the wheel off the bike, switch your gears down to your smallest cog and then pop the whole wheel right off. You can let the remaining air out of your wheel by using your hands to squeeze around the tire. Use your hands to pull the tire back away from the rim so to break the seal between your tire and http://www.xmapexsport.com/frame-c1770.html the rim, and now stick your tire lever between the metal rim and your tire and then pull the tire lever all around the rim so that the sides of the tire are no longer held by the rim.
Now with the tire off, look for the stem of your tube which will be inserted into the rim. It may be held in place by a bolt, in which case will need to take the bolt off and pull the tube right out and off the rim.
At this point it is a good idea to lightweight bicycles take the time to find out whether or not there are any sharp objects in the tire, including rocks that could be inside. You can do this by running your hand inside the tire but do it slowly and be careful so as not to cut yourself on anything.
Okay, now pump some air back into your faulty tube and try to find the leak. You may be able to see the air leaking out, or at least hear it. If not, you can try running your hand over the tube and feel for leaking air. If both these methods fail, then you only have a small puncture and you will need to get a bucket of water and dunk the tube into the bucket and watch for bubbles.
Once you have identified the leak, take your patch kit and read the instructions on how to use it. Follow the instructions accurately so that the patch holds. If the hole is too big to be patched, then just throw the whole tube away and use your new replacement tube.
Blow a little bit of air into http://www.xmapexsport.com/wheel-c1768.html your replacement tube or newly patched tube so that it takes shape. This is important so you don't have it lying flat inside the tire after you put it back and it will allow the tube to be inflated easier.
Now with the bit of air inside the tube, begin putting it inside the tire and around the rim as you previously had it before, including putting the stem back in place. Put your tire back on, and use your hands to tuck the tire's edges back into the rim, being careful no tubing is sticking out. You will likely need to use the tire lever to help finish the last part of this job.
Lastly, use your CO2 cartridge or a pump to pump air into your tire and your mountain bike is now ready to hit the trails again. Great job! If you feel you need a visual, go to YouTube as there are plenty of real life demos out there to watch.