As you progress through the game, you'll begin to come across generators more often in enemy bases. You can find a permanent spawn of a generator in the Main Mission
La Carcel Del Pueblo in
San Mateo, if you need to.
Next, make sure you by the
C4 skill, and cycle through your items using left on the D-Pad until you have it selected. Sneak into the base, open the gate to the generator, throw the C4 on the generator and then explode it to earn the achievement.