Drassen is most likely the first city you need to liberate. When attacking, enemy forces should be light, with only 6-8 enemies in each sector. It provides an airport, as well as the first supply base for the rebels.
In sector B13, there are three enemies that are outside of the fence. One is at the guard post, while two more are near the building to the east. Inside the fence, additional enemies will approach from the airplane.
In C13, enemies tend to cluster in the main road between the buildings, but there may be a straggler near the sweatshop.
In D13, enemies should be visible when you approach the church.
As you can learn from Waldo (in the Drassen Airport), the helicopter is functional, but needs a pilot. He suggests looking for one in the swamp, and Skyrighter may be found in any of the sectors B15, C16, D12, and E14.
If you control the airport, you will get access to the helicopter. It is initially expensive due to danger, but
Conquering the airport also lets you purchase items from Bobby Ray's. This is available from the laptop menu, and by visiting A.I.M. and opening the Links section.
In C13, a woman named Doreen controls a sweatshop, and the locals want her gone.
If you have a mercenary with a high leadership skill, you can talk to her using friendly dialogue and convince her to leave. This path gives a slightly better loyalty score.
If no mercenary is a leader, then you will have to kill her to gain support. The loyalty gain is slightly less, but you can obtain the key to where MP5K is stored.
Food for Rebels
The rebels directed you to Drassen for food.
Look for Father Walker, who is either in the church at D13, or in the bar at C13. You can speak with him to setup a food convoy, but some mercenaries may need to provide him with a drink first.
There is a SAM-site at D15. Liberating the site allows you to safely use the helicopter.