How to change a tyre
Firstly completely deflate the tyre. This will allow you to push the beading away from the rim, (see picture) and create enough slack to insert your tyre lever.
To create extra slack, work around the tyre pushing the beading into the central channel in the rim.
Insert the tyre lever under the tyre beading ensuring not to catch the inner tube. Holding the wheel upright and pushing the tyre lever away from yourself, run the tyre lever all the way round the rim. Half of the tyre will now be free.
At this point you should be able to pull the second half of the tyre off the rim. If the tyre is stiff then reach in and carefully pull the inner tube out first, creating more slack in the tyre.
You may need to help the second half of the tyre off using your tyre lever.
To fit a tyre reverse this process. Install the first half of the tyre onto the rim with the tyre logo aligned with the valve.
Gently inflate the tube so it takes its shape, insert the valve through the valve hole and tuck the tube into the tyre.
Push the tube into the central gully of the rim, then start hooking the second bead of the tyre onto the rim.
If it becomes tight, push the tyre from side to side on the rim to create some slack and release a little air from the tube.
Double check the tyre is properly seated on the rim all the way round, then inflate the tyre checking as you go.
The recommend tyre pressure will be written on the side of the tyre. Generally, higher pressures will create less rolling resistance, and lower pressures will provide more grip, depending on application.