Facebook has recently launched support for Nepali language. You can follow the steps below to use Facebook in Nepali:
1. Go to Settings (Top right corner, next to your name)
2. Go to Account Settings
3. Click on the Language tab
4. From the drop down menu next to Primary Language choose नेपाली. (You might have to scroll all the way to the bottom)
Click here to go to your Facebook Account Settings page now. You must be logged in to make this change. The images below depict the process of making this change.
Your Facebook page will look like this after you make the selection.