This method worked for me:
http://www.everythingdiamond.info/showthread.php?t=387
You need to use a file editor such as Total Commander, so download and install that first:
http://ghisler.fileburst.com/ce/tcmdpocketarm.cab
1. In Total Commander, navigate to the Windows directory and find 2330fc3c_manila. Copy the file OUT of the windows directory. Go to the properties of that file and uncheck "Read only". Click ok to save your changes to the file. Copy the file BACK to the Windows directory.
2. Download Weather Database Editor (attached in this post) and install. Launch the app, go to your Country > click "Edit" > click "Cities" > click "Edit" > click "Add City".
3. Add your city using the Accuweather code. Example for me: NAM|CA|NB|FREDERICTON (Continent|Country|Province|City)
4. Click OK to save that bad boy, and then soft reset your phone.
5. You can now add your city in TF3D and pray for sun.