To unlock this you'll need to complete 9 of each of the following side missions:
Vehicle Drop Off (Breach and clear a building then hack a computer)
Guns For Hire (Grab a sicario leader and intimidate him)
Mortar (Start a radio up and defend it for 2 or 3 minutes)
Diversion (Turn off an antenna then turn off a second one within a time limit)
Spotting (Tag a care package)
Just a few tips for the more difficult missions: When defending the radio in the Mortar missions, make use of the ability to call in rebel reinforcements from the command wheel (Hold
), and before you start the mission, try to block off some roads with a vehicle and place mines along the roads to make it difficult for enemies to reach the radio.
For the diversion missions, find a helicopter before starting the mission and just use that to reach the second antenna, rather than the vehicle provided.