To see a sample of one font on a Datadisk terminal, R DDFONT and give it
  the name of the font (e.g. "NGR30").  Say HELP DDFONT for more info.
To print a sample of a particular font on the XGP, say
  R FCOPY;<file name>/INFO/SAMPLE.  Say HELP FCOPY to learn more of its
  capabilities.
To print a sample text on the XGP in a number of different fonts for 
  comparison, say R FSAMPL.
To make a .TFX file for an existing font (needed if and only if you want
  to use this font with the old XGPTEX document compiler), say R TFXGEN.
  To edit .TFX files, use TFXPR and TFDRD.  Say READ TFX for more info.
To make a .TFM file for an existing font (needed if and only if you want
  to use this font with the new TEX document compiler), see TFM.TXT[tex,sys].
  To edit .TFM files, use TFTOPL and PLTOTF.
To examine or edit characters in an existing font, use EDFONT, described
  in EDFONT.TVR[UP,DOC].
To edit the characters of a font using E, use FMUNGE, described in
  FMUNGE.REF[UP,DOC] or FNTCHR/CHRFNT, described in FNTCHR.MAI[UP,DOC].
  FMUNGE is probably easier to use; FNTCHR/CHRFNT were designed for use
  with the METAFONT system.
To create a new font use TVFONT, described in TVFONT.BGB[UP,DOC], or
  PIX, described briefly via HELP PIX.
To scale the size of a font use FSCALE, described in FSCALE.DON[UP,DOC].
To combine selected characters from two fonts, use COMBIN (say HELP
   COMBIN for description).
To compile a font, RUN UFC[XGP,SYS].  UFC.REG[UP,DOC] explains what
  compiling a font means, and why it's good for you.
To poke at all sorts of mystic parameters in a font file (not recommended
  unless you know what you're doing!), R FONT.  FONT.BH[UP,DOC] is the
  documentation file for this program.  One warning in particular: Using
  FONT to find out the height or width of a few characters (using the
  "modify chars" option) will cause the file's last-written date to
  change, obsoleting the CFT (compiled font) file for that font.  Make a
  copy of the file and look at that instead.
To learn about the format of font files, see FORMAT.DOC[XGP,SYS].

Some of the above programs append the ".FNT[XGP,SYS]" if you leave it
  out, but all of them (I think) will accept the complete file name if
  you type it all.

To create an XGP font using Knuth's Metafont program, see
  MANUAL.TEX[MF,DEK].  Hardcopy documentation is available in the TeX and
  Metafont manual available from Digital Press, or HELP MF.