For most Linux distributions, emacs is able to display Belarusian
characters out of box. However, the following conditions should
satisfy:
Cyrillic iso-8859-5 fonts should be properly installed.
Emacs-mule package should be installed.
The user may want to change the default keyboard layout ("input
method" in emacs slang) to jcuken. This feature is provided by
belarusian.el along with some other goodies. Read the comments
in the beginning of belarusian.el for details.