Check out this nifty web site that will tell you how.
There are also certified persons in most states who will install your car seats free of charge. In Fairfield County CT there are a few firemen in the Stamford/Greenwich area who are certified to do this and they hold clinics a couple of times per month. We were shocked when we had them install the infant seats in our Hyundai when the boys were little. It was incredible to see the lengths they went to in order to make sure those stinking bases stayed in place on the back seat. Picture large fireman type kneeling on top of the car seat base in the tiny backseat of our Hyundai hatchback while fireman type number 2 snaked around him to insert the seatbelt buckle into the recepticle. We were never able to replicate it.