On the Lastra Forest map, you will see 2 sets of door sections that split the path ahead and you can only choose one of the doors each time to progress.
The achievement requires you to try each door total.
In order to obtain this achievement only running the dungeon 3 times, follow the pattern of;
First Section:
LEFT Second Section:
LEFT
First Section:
RIGHT Second Section:
RIGHT
First Section:
ANY Second Section:
MIDDLEThe achievement will pop after you move through the 2nd door and move up into the wider area above. You do not need to finish the dungeon completely and can port out once the achievement for each door has popped.