Load the game, and select the 'Moon' level in free play.
For this one, you're trying to recreate the achievement picture, which shows a lander, a flag, and two astronauts. (You'll also need a camera.)
Make sure you're in 'build mode' rather than 'drive mode' (press
if needed), then press
to open the spawn menu. All the items we need are in the 'sci-fi' row, which is right at the bottom of that menu.
From the sci-fi row, spawn a lunar lander (12th on the row)
Spawn a camera (22nd on the row) facing the lander's ladder. Use
to rotate it if needed.
Next spawn a flag (23rd on the row) and two
EVA suits (far right of the row) near the lander.
to stop spawning items, then hover over the camera and press
to take a picture.
As long as you have the lander (with ladder visible), flag, and two astronauts in view of the camera when you press
, the achievement will pop.