Using custom created bitmap font in photoshop?

I'm creating custom bitmap fonts in GlyphDesigner for game development. GlyphDesigner (and BMGlyph for that matter) outputs both a .png file and an .xml or .fnt, depending on output setting. I'm not able to find any info about how I can convert these 2 files into a installable font to add to Photoshop, so I can create design mockups using our custom bitmap font. Is this not possible? I've found converters for .fnt to .ttf, but those are expecting a single .fnt file with all the data compiled to one file- seems I'm missing a step in how to convert my 2 files into a single .fnt file.  Is there any way this is possible?