First, you have to unlock Bilbo Baggins either by purchasing him in the Shire or by entering the code into the extras menu. Codes DO NOT disable trophies.
Bilbo unlock code: J4337V
Next, you will want to fast travel to Weathertop (night or day does not matter). Then walk towards Rivendell. Once you enter the Trollshaws area and walk around a little bit the trophy should pop.