The game isn't overly clear about these. In short you'll need to complete all of 1 type of Rebel Op
There are 4 types of Rebel Op's exclusive to this DLC - Sabotage, Rebel VIP, Headhunter & Towers. There are 4 of each in the checklist, spread across 3 regions - however you'll only see 3 of each on the map. That's because the 4th is a "final op" for completing the rest of 1 type of Rebel Op.
This will come naturally when working towards "Thorough Supporter" as you need to complete every mission & rebel op anyway, so there is no need to go out your way for this achievement.