In the Isla Nublar Visitor Center, on the left side of the room is a door with DNA above it. In here, go up to the computer and you can create your dinosaur. You should be able to get here sometime after unlocking the triceratops.
Now choose you dinosaur and customize how you want, or just hit the randomize button. Now hit
to back out and the achievement should pop.
If you want to know where the Visitor's Center is from the helicopter, just follow the path the sign takes you on until you reach the big dome-like building with stairs leading to the entrance.