When you enter the surgery area of the medical pavilion stay to your left and you will run into your first hackable turret. Hopefully you have enough plasmid to where you can shock the turret to prevent it from firing at you. Otherwise you will be taking some damage. Run up to it and hit
and hack it like you did with the vending machine and security bot. It will be a little harder since there will be broken red pipes. Otherwise it is not that hard once you understand it. It should unlock when you finish the hack.
*IMPORTANT If you did not get your achievement right here, check the progress tracker. If there is no progress for that or any of your audio diaries collected, start a new game. The game might glitch for some people. I have hacked several bots, cameras & vending machines but nothing unlocked or made progress. It was at this point I started a new game, got to here and it unlocked right away.