Port #1 is Supply (pressure from the bottle).
Port #2 goes to the shifter.
Port #3 is the exhaust.
Electrical connections should be +12V. on pin #1 & ground on Pin #2.
As a test, connect wire from pin #2 to ground & touch wire from pin #1 to a +12. The valve should energize. If the bottle is connected to port #1, you should get pressure out of port #2.