Translation:At the left side of the building, go down.
Alrighty having discussed this with indonesian hubby. You need to say "turun ke bawah" to mean go down (even though "turun" means down anyway). The same for "naik ke atas" is used when you want someone to "go up" (upstairs etc). You can't use just "turun" or "naik" on it's own for this example.