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.
Press
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.