Subaru 1998 Impreza Owner's Manual page 279

J Wheel covers (Locking type wheel covers)
B Removing the wheel cover
CAUTION
If it becomes necessary to remove the wheel cover, NEVER use a
screwdriver or other prying tool. Doing so will severely damage
or destroy the wheel cover.
Grasp the wheel cover with both hands by the spokes and twist
sharply in a counterclockwise direction until you feel the detent
release. Now the wheel cover is free from the retention ring.
B Installing the wheel cover
1. Install the wheel cover on the retention ring, aligning the valve stem
with the valve stem area and fitting the lock pins on the wheel cover
with the lock springs in the retention ring.
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HG0105