There are various input methods available for Linux, yet I'll just stick with Slackware's good old default: SCIM. SCIM is official package in Slackware64. So installing the packages is pretty classic.
#installpkg ./slackware64/x/scim*.txz
Also make sure you are using UTF8-capable locale. Check /etc/profile.d/lang.sh for something like this:
export LANG=en_US.utf8
Enable SCIM script(s) in /etc/profile.d/ too
chmod +x /etc/profile.d/scim*
--anyway, is the anyone out there using csh in their daily mortal life?