Once you've unlocked Seize, you can use it to get an enemy fighting on your side. Chip their health down until the
button prompt appears, and hold it down until they're under your spell. Do this 10 times to get the achievement.
Unlocking A Captive Audience missionYou'll need to clear the side mission
A Captive Audience. The mission is unlocked by finding a collectible report 'Astralnauts Information'. It's in Parapsychology, in an office right of the fast travel point. Look on a filing cabinet.
Unlocking SeizeYou'll need to cleanse the X-ray light box found during
A Captive Audience. It's in the Hypnosis Lab. Follow the mission prompts. At one point you'll need to solve one of the cube password puzzles to open the door to the X-ray box. The shape you need is stuck to the glass behind the computer screen.