That depends on exactly what Jeep you have. Most 96's were the Quadra-trac system, in which case you are in 4 wheel drive all the time! To put it in low range (For only the nastiest conditions- dont use this for normal driving on the street) you need to stop the vehicle, put it in nuetral, and pull the transfer case lever (next to the shifter) firmly and quickly to the "4LO" position. If you have a "select trac", i believe you just pull the lever to 4 wheel drive, and away you go!
The 4 wheel drive switch is located on top of the transfer case
A Grand Cherokee is either rear wheel drive or four wheel/all wheel drive.
The 2010 Jeep Grand-Cherokee has rear wheel drive.
The 2006 Jeep Grand-Cherokee has rear wheel drive.
The 2003 Jeep Grand-Cherokee has rear wheel drive.
The 2011 Jeep Grand-Cherokee has rear wheel drive.
The 2005 Jeep Grand-Cherokee has rear wheel drive.
The 2007 Jeep Grand-Cherokee has rear wheel drive.
The 2009 Jeep Grand-Cherokee has rear wheel drive.
The 2013 Jeep Grand-Cherokee has rear wheel drive.
The 2008 Jeep Grand-Cherokee has rear wheel drive.
The 2004 Jeep Grand-Cherokee has rear wheel drive.