To get the Stud Magnet Red Brick, you'll need to go to the Carnivore section in the Jurassic Park world (it's blow the T-Rex section). There you'll need to help the ranger find 3 lost eggs.
How to find them:
1. One is behind some reeds you'll need to cut down. It's located by the amber piece.
2. Use a customized dinosaur, that can use roar, to break down a piece of amber.
3. Break a machine on the side of a fence with a Raptor, then use a female character to
swing up to the egg.
As Arador pointed out, you'll need 30 Gold Bricks before you can use the Custom Dinosaur Platform for #2.
Once you have the red brick, return to the Visitor Centre and unlock it (it cost 100,000 studs). Pause, go to Extras, turn it on, and there's your achievement.