I found out last night that using sprite fonts in Monogame is not as straightforward as one would hope at the moment. The solution that I needed to use was enumerated here: Loading a font using Monogame
In short, you need to:
- Download and install Visual C# 2010 Express.
- Create an XNA project.
- Add your Sprite Font using the Add > New Item menu option on the content project.
- Compile the probject. This should build an .xnb file.
- Go to your Monogame project and import that .xnb file using the Add > Existing Item menu option.
- Set the build action to Content and set the Copy to Output Directory accordingly.
Regarding that last point, if you add the .xnb to the project as a linked item you can go back to your VS 2010 project and recompile the sprite font with any changes that you might require once you test the font in your Monogame project. If you go this route make sure that the Copy to Output Directory property is set to "Copy if newer." This scheme would allow you to compile some various .xnb assets and keep them in a global repository for use in other games, assuming you "set 'em and forget 'em."