Watch Dogs: Legion has a pretty unique feature which is not only new for the franchise, but for the gaming industry as well. That is, being able to recruit any character and swap into them at any point in the game. If you are looking to recruit Operatives in the game, there are a number of ways to do so.
Some of the Operatives unlock as you progress through the main campaign. For instance, in one of the missions you are required to recruit a construction worker in order to get hold of a cargo drone. Likewise, other missions require you to recruit operatives with specific skills and you unlock them as you progress through the game.
Another way to unlock Operatives is by just walking to any of the characters in the game, and pressing the Recruit button. This will trigger a chain of missions for that particular character. You can complete them and after that, you will get the option to recruit them. Depending on their outlook towards DedSec, they might agree to join you.
Last but not the least, some Operatives are unlocked by making boroughs defiant. You can read our guide here to know more about it. This will give access to Specialized Operatives which have a special set of skills and are way more skilled than normal characters in the game.