GMC 2003 Envoy XL Owner's Manual page 55

3.
,
Pick up the latch plate, and run the lap and shoulder
portions of the vehicle's safety belt through
or around the restraint. The child restraint
instructions will show you how.
4. Buckle the belt. Make sure the release button
i s
positioned so you would be able to unbuckle the
safety belt quickly if you ever had to.
1-48