You have to take apart the dash and the glove box. It bolts in, but before you do any of that, you have to disable the system, and the procedure for that is in the FSM.
98 Riviera SC3800 All stock except gutted air box.
1970 Buick GS455 Stage1, TSP built 470BBB, 602HP/589TQ
Best MPH, 116.06 MPH, Best ET, 11.54