Edit the Dtterm resource file in the /usr/dt/app-defaults/language directory.
You can use either the class name (Dtterm) or the application name (dtterm) for a resource file of Dtterm.
Also, setting the LANG environment variable alters the search path of resource files to include the /usr/dt/app-defaults/language directory, where language is the locale name.
After setting the LANG environment variable, the search path for resource files would include the following two folders:
Insert the font set you want to use at the bottom of the file.
For example, to use a monospace font, put this line at the bottom of the file:
dtterm -fn -dt-interface user-medium-r-normal-*-*-*-*