A major component of the mountain bike is its inner tubes and the process of changing them is also quite similar to the ordinary bikes. The only major distinguishing factor is how it is attached to the rest of the bike as well as its size as compared to the normal bikes. This is because the tyres remain attached to derailleur and the chain wrappings with multiple gears. First, you need to turn the bike upside down and then loosen the axle nuts, remove a brake shoe or simply loosen the cables of the brakes a bit.
Secondly, carefully remove the tyre from the bike by slightly twisting it, if it is connected to the derailleur. Then using the flat blade screwdriver, remove one side of the tyre from the rim. Then place the screw driver between the rim and the tire bead and slowly cover the circumference; by doing so, the entire bead will be separated from the rim at some point. Then install the new tube and simply reverse the above procedure. Lastly, just place the wheel in its appropriate place and then tighten all the axle nuts on it.