Vehicles Guide
First off, having acquired a vehicle, right-click on the key and select "use". This registers the vehicle to you. Head outside your relevant city, and you should see a large structure marked as "ASG Warp Garage". Select your vehicle and press the "Spawn" Button. The vehicle should now appear somewhere nearby. ASG's are notoriously random and it may require some searching to find you vehicle. If you cannot find it, it may have been spawned undergorund - just dismiss and respawn.
Use your vehicle once you have located it to enter. For anyone who has played UT2004, you should feel immediately at home. If not, you go into thrid person on entering the vehicle. For ground vehicles the controls are nice and simple. Foward drives the vehicle fowards, strafe left rotates left, strafe right rotates right and backwards reverses. The flying vehicles I will leave descriptions to those more experienced. If you are gunning, it works much the same as any other weapon - line the crosshair up, wait for the reticle to close and let rip.
One note - don't take ground vehicles - even hovertecs - into water. They stop dead and reset to the ASG very quickly. To put your vehicle away, ensure it is in the same sector as a warp garage, use the garage and select dismiss.