Star Trucker

The game will make you do this as the first part of the tutorial should you choose to play it. But I'll explain how to do it outside of the tutorial's context.

Any time you bump into objects in space, be it debris, stations, other trucks, signs, cargo... anything besides more space really... your truck's hull will be damaged, if damaged enough then a hole may pop up and leak your very important air, "Lung juice" as a fellow trucker might call it. This is what the achievement wants fixed up. The left monitor should have a red light on the hull integrity screen should there be any holes to fix and it will beep at you until you go repair it.

Since the damage is outside, you will need to look down in first person mode and get up from your chair, then head in the direction of the airlock located at the top back of the truck's interior. Make sure to grab your space-suit sitting near the door in a charging dock before heading out or you will have a bad time. With the suit on, hit the air-lock button on the right (it's next to the suit's location) and walk in. Turn around and hit the matching button located to the right to seal the airlock. Now to the left pull the lever and be sent outside.

Once outside in space, you can see markers on any holes your truck may have at the moment. The markers look like wrenches in a box if you need help spotting them. Move on over to one and you will get a prompt once close enough to the hole, hold the button down to patch it up and you are good to go!

I think you only need to fix one hole to get the achievement, but go ahead and fix them all up before heading back to the airlock at the top of the truck.