Gu10 light bulbs--more appropriately called lamps, as their structure differs from a standard bulb--are usually quartz/halogen, although LED versions are available for some fixtures. Modern track lighting and other ceiling fixtures use these lamps to produce a bright white light with a moderate beam spread. Unlike halogen lamps with a simple two-prong base that pull straight out of their sockets, gu10 lamps have a cylinder at the base of each prong are wider than the prongs that connect the lamp to its socket.
Stand on a ladder so you can comfortably reach your light fixture.
Press the existing Gu10 lamp into the fixture using both thumbs.
Turn the lamp counter-clockwise as you continue to press inward, using the pressure of your thumbs to grip the bulb.
Release your pressure on the lamp when it won't turn any farther.
Pull the lamp straight out of the socket. You may need to wiggle it gently to get the cylindrical "feet" aligned correctly with the larger openings in the socket.
Discard the old lamp and remove packaging from your new lamp. Line the prongs on the new lamp up with the wide openings on the socket.
Press inward on the edges of the new lamp with your thumbs and twist the lamp clockwise as far as it will go.
If your gu10 lamp does not have a glass cover across the front, be very careful to only handle it by the reflector. If oils from your fingers get on the inner lamp, they can cause it to heat improperly and explode.