For the under-hood fuse box (power distribution center): This is usually located near the battery, often on the driver's side fender well.
For the interior fuse box (passenger compartment fuse panel): This is typically found under the dashboard, on the driver's side. You might need to remove a small access panel or part of the dash trim to reach it. It's often located below the steering column or further down towards the left knee area.
To be certain: Your best bet is to consult your owner's manual. It will have a diagram showing the exact locations of both fuse boxes and label each fuse. If you don't have the manual, you can often find a PDF version online through a search for "1992 Dodge D150 owner's manual". A search using the specific trim level (e.g., "1992 Dodge D150 regular cab owner's manual") might yield even better results.