This is easy...:
Boost Gauge Installation Dodge Cummins Turbo Diesel 1991-1998 12 Valve (Intercooled) - the above pic is of a first gen 12V, the procedure is the same for a second gen 12V.
1. Locate and remove the 1/8" NPT pipe plug (see pic) on the driver's side of the intake manifold.
2. Install the fitting and connect the hose making sure that the hose fits snug but does not pinch.
Alternately, you can drill and tap the intake manifold.