As you enter the level, search the first corpse you find to pick up your first Enzyme sample and pick up the audio log before proceeding through the door.
Follow the tunnel round and enter the Farmer’s Market. You’ll see a Houdini Splicer who will probably be killed by the rocket turret off to the right. Go and hack the turret and then head back past the Cheese Shop where you’ll find a security camera round to the right, near the ceiling.
You can use the oil slick to burn a Splicer and then take out the turret in the Meat shop before grabbing all the pick ups. Through the next door you’ll run into a Big Daddy and Little Sister. Let the Big Daddy kill the Splicer before taking him out. There are explosive cylinders you can use to make the fight go easier. Watch out for a security camera in the shop ahead and more Splicers as you search for pick ups, there are some hidden areas here too.