Hi,
Check here:
http://www.coscojuvenile.com/usa/eng/DJGFiles/ProductDocuments/43583614D.pdf
Hope this helps.

First, contact Cosco (contact info here) to get a new manual.

You can install the seat EITHER with the LATCH anchoring system OR with a seat belt. Neither is safer than the other, but LATCH is meant to be more convenient (if your car is new enough to have LATCH anchors.) You can't use both the seat belt and LATCH together to install the seat - it seems intuitive that it would be doubly secure, but it can cause enough stress and force on the plastic to damage the carseat.

To install rear-facing with LATCH (until your little one is BOTH one year old and 20 pounds at the earliest...it's safest to stay rear-facing until the seat's rear-facing limit of 33 pounds or until the little ones head comes to the top of the back of the seat):
Place the seat rear facing in the back seat of the car. If your car has LATCH capability, there will be little U-shaped metal anchors in the seat's crease, where the back and bench part of the seat meet. Check your car's owner's manual for locations - some cars only have them for the outer seats, not the middle. There should be a long black strap with hooks on both ends attached inside the carseat, usually inside one of the seat belt paths (the holes near the front on the bottom for rear-facing; holes on the sides of the back of the seat for forward-facing...there should be stickers labeling them). Pull an end of the LATCH strap out of each side of the belt path and hook the hooks to the LATCH anchors (one on each side of the car seat). Kneel in the car seat and pull the extra length of the strap to tighten. It's tight enough when you can pull on it (side to side) at the belt path and it doesn't move more than 1 inch. It IS normal to be able to take the top of the seat and pull it back towards your car's seat back, so don't worry about that, just the movement at the belt path. You do NOT use the top tether strap when rear-facing, so just leave it bundled as it is.

To install it rear-facing with the seat belt instead of the latch, again, place it rear facing in the seat. Pull the car's seatbelt out and place it through the rear-facing belt path, being sure it doesn't twist. Buckle it, then kneel in the seat to tighten. Pull the seatbelt ALL of the way out from it's feeder and thread it back in, so that it catches and doesn't loosen. Check for tightness as above.

Another important installation tidbit - When you have the seat rear-facing, the harness should come out of a slot even with or BELOW your child's shoulders...for a forward facing seat, it should be even with or ABOVE the shoulders.

For forward facing installation with LATCH, pull the LATCH strap ends out of the belt path holes on the back of the seat (again, see the stickers on the seat to find the proper belt path). Place it in the seat where you want it and hook the hooks to the anchors, just like we did above. Again, kneel in it and pull tight. The top anchor strap (similar black strap, but with only one hook, and attached near the top of the seat back is used to prevent the top of the seat from moving forward. Once the LATCH is tightened, take that hook and hook it to your tether anchors (either behind the seat in the rear dash board or low on the back side of the seat - again, check your car's owner's manual if you don't know for sure where they are.) Pull it tight. Check the side to side motion as above - you should also not be able to pull the carseat forward from the seat.

Forward facing installation with a seat belt - Place the seat forward facing in the seat you want it in. Pull the car's seat belt out and thread it through the belt path on the back of the carseat, making sure that it doesn't twist. Buckle it, pull the seat belt all the way out of the feeder and then feed it back in, kneeling in the carseat to get a tight install. Attach the top tether strap and check side to side motion as above.

Cavaliers 2002 and older have whats called a "locking Latch Plate" Its on the buckle part of the shoulder belt. The rear seats in these cavaliers do not have the child safety mechanism in the shoulder belt that causes it to lock after you pull it all the way out! This latch plate has been required by law since 96, they added a new law in 2002 for 2003 vehicles that requires an anchor in the seat. My 2002 was the last year made with the locking latch plate, 2003 switched to anchors. When the lower buckle and the shoulder belt are COMPLETELY STRAIGHT together, it automatically locks. you should be able to pull the shoulder strap to tighten the seat in, but you should not be able to loosen the car seat in the strap (wiggling it). If it comes loose the belts are not straight. Every carseat that I've used has required me to rotate the bottom buckle twice and then twist the top buckle twice in the opposite direction, then buckle them together, to get it straight because the bottom buckle is too long. Its really confusing and very easy to get it wrong. Take your carseat to a carseat check station. In texas they do it at the department of motor safety. In arizona they can do it at the fire department...just look around on the internet you will find one!