I tried the following things:
1. I installed the Bitmap Font Generator.
2. I set Export Options / Textures to png.
3. When saving with "Save bitmap font as", two files (png file and fnt
file) were created.
4. Then I put the two files in "res: //" on a project on Godot Engine.
After this, I do not know how to set it to display Bitmap font in Godot Engine. :’-(