Buick 1993 Roadmaster Owner's Manual page 270

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Unskrew
.tht$wingnut. From
outside the vehicle,,
carefully pull the taillight assembly away from the body.
Press the bulb housing release lever and turn the housing
1/4.turn counter-clockwise (to the left) to remove it..
To remove the bulb, push it
in
and rotate it
counterclockwise(to the left).
Reverse all the steps to reassemble the taillight housing.