This is a story related achievement which will unlock with natural story progression.
After speaking with Bluto you will need to make your way to Finley's boarding house. Once you arrive talk to Finley, he will tell you that you can access the first floor by building a ladder from the broken parts under the stairs.
You will need to collect the following items to build the ladder and to access the room:
- Elbow Pipe
- Hammer Head
- Perfume Puffer
- Lead Pipe
- Little Stick
- Nozzle from a Perfume Atomizer
- Wooden Pole
- Two Sticks
- A hammer
Once you have found these items you will be able to combine them within your inventory to build the ladder. The other ideas you have collected you will need to use to access the room above.