Start with a search..............(of this forum)
Then go here
http://www.forabodiesonly.com/mopar/showthread.php?p=1970088617
and download yourself a service manual. Probably for 71, a 70 manual is the closest.
Do ANY of the lamps work, IE shift indicator, radio, heater bezel?
"The thing" about dash lamps is they are a "trick"
The headlight switch has two voltage sources, we are interested in the TAIL LIGHT FUSE which must be good. The headlight switch must be on in tail / park or head
So make sure your park / tail lamps actually WORK
The dimmer control must be twisted to the left
and now power comes out of the dimmer and goes TO the inst fuse in the fuse box. This is the smallest fuse on one end of the panel.
With the above conditions, check for power at the inst. fuse. You should have power at both ends of the fuse.
All dimmer controlled dash lamps receive power off one end of that fuse on ORANGE wiring.