This is the Font Editor.

Use the arrow keys to highlight a font character, and press ENTER or SPACE to start editing it.

While editing a font character, use the arrow keys to select pixels and press SPACE to toggle them off and on. When you are finished, press ENTER or ESC.

It is generally a good idea to leave the right and bottom rows of pixels blank to prevent characters in strings of text from running together.

You can export your font as an OHF file, or import a new font from OHF files that you download from other people.

The OHF font format is only used by the OHRRPGCE. There is no way to import other font formats like TrueType TTF.