WordPerfect doesn't properly support Unicode, so there aren't many workarounds. One which sometimes works is to open up the Character Map utility and copy and paste the character you would like from the character map to your WP document; but it sounds like you've tried that, and, yes, WP's extended character handling is atrocious. Sadly, full Unicode support doesn't seem to be a huge priority for them, as it would break the way their program works internally, due to some shortcuts taken a decade ago. If using ligatures is important and not using MSWord is also important, you might want to consider OpenOffice...
Alex the fellow WordPerfect user...