Easiest way for me is to:
Have font installed on machine and include the font (.TTF) in the Files folder in you project (right click files and import).
Pick same font in the font settings and when you export make sure the file-name is the same including case as C2 exports everything as lower-case (you have to manually edit the export). This works for CocoonJS.
For my font it was called Tw Cen MT with a style of Condensed Extra Bold. The final file-name is : Tw Cen MT Condensed Extra Bold.tff