Pontiac 1998 Grand Prix Owner's Manual page 54

5. Push the latch plate (F) into the buckle until it clicks.
Be sure the buckle is free of any
foreign objects that
may prevent you from securing the latch plates. If
you can't secure a latch plate, see your dealer for
service before using the child restraint.
6. In a single motion, pull the other side of the harness
all the way out. Keeping the harness pulled all the
way out, place it over the child's shoulder.
4.
Select only one side of the harness. P u l l the lap part
of the harness out, and place the harness over
the
child's shoulder.
If both sides of the harness are pulled out, the lap
parts will lock. If the lap parts lock, let both sides of
the harness go back all the way so each side will
move freely
again.
Then repeat this step, pulling
only one side of
the
harness out.