Add fonts to directory ~/.fonts
.
See available fonts:
$ fc-list | col | sort | less
For example, among all I have:
/home/riccardo/.fonts/iosevka-term/ttf/iosevka-term-regular.ttf: Iosevka Term:style=Regular
Add the following to '~/.Xdefaults':
XTerm*faceName: Iosevka Term
XTerm*faceSize: 15
Reload resource file and run xterm:
$ xrdb ~/.Xresources
$ xterm