You'll unlock this achievement with natural story progession, so don't worry about missing it!
So for this achievement you need to gain access to an apartment on the first floor, you'll need to find a bunch of items so that you can assemble a makeshift ladder, here's a list of the items you'll need;
• Elbow pipe
• Hammer head
• Perfume puffer
• Lead pipe
• Little stick
• Nozzle from a perfume atomizer
• Wooden pole
• Two sticks
• Nails
• Rags
• A hammer
The locations of each of these can be seen in the video below.
Once you've assembled the ladder and used it to climb up to the apartment on the first floor the achievement will unlock!
If you find yourself stuck on a particular part of the game be sure to check out this excellent video walkthrough of the entire game, the users youtube channel can be found here;
http://bit.ly/ih2LIC. Alternatively I've linked in the first video below and you can use that to reach his channel.
* Credit to adventuregamefan for the video