How doo u get the little rocketman achievment?

After you come out of the tunnel and find the small Shack were Alyx communicates with the Rebel Base, use your Gravity Gun to pick the small Gnome under the bed to left of the terminal Alyx is talking into. You must carry him throughout the game, putting him down when necessary, usually to fight. When you get the car, you have to Jam him into the back, in between the two bar right above the cushioned seats. It can be hard, but you'll get it. Now, you need to driver all the way to the Rebel Base, and take the Gnome with you. When you first meet the scientist working on the rocket, there will be a small door open. This is where you put the Gnome in. Once you launch the rocket, you should get the achievement.