The yaw is controlled by the swept wing design of the glider. As a hang glider flies, it sinks through the air. If that air is rising faster than the glider sinks, the glider goes up. This rising air is called lift. Without lift a hang glider sinks at about 150 feet a minute, so it depends on how high you are.
Most pilots like to fly in lift.
A normal flight in good thermalling conditions will last about 2 or 3 hours. To foot launch on a slope you hold the glider in the proper position, and smoothly accelerate the glider to a run. When you reach the proper air speed the glider will lift you off the ground. When you're first learning to fly you will simply roll in on wheels connected to the cross bar of the glider. After a few lessons on the hill you will begin to learn how to flare the glider and land on your feet.