To find it, I recommend:
1. Consult your owner's manual: This is the best place to start. The manual should have diagrams showing the location of all sensors.
2. Use a repair manual: A Chilton's or Haynes repair manual specific to your year and engine will have detailed diagrams and descriptions.
3. Look online: Search for "[Your Engine] 1995 Chevy Truck MAP Sensor Location" on Google Images. You'll likely find pictures showing its location on similar trucks.
4. Look near the intake manifold: The MAP sensor is usually mounted somewhere easily accessible on or near the intake manifold. It's a small, usually black, rectangular or cylindrical sensor with a wiring harness connected.
Caution: Before attempting any work on your vehicle, disconnect the negative terminal of your battery to prevent electrical shorts or damage.