Conkeror doesn't yet have any special spellchecking commands or UI.  You can enable Mozilla's spellchecker with the pref layout.spellcheckDefault.

http://kb.mozillazine.org/Layout.spellcheckDefault

Also see http://kb.mozillazine.org/Spellchecker.dictionary

Or, make sure you have emacs set up for external editing in conkeror and just use emacs' spellchecking [if supported by your system].

= See Also =
[[http://thread.gmane.org/gmane.comp.mozilla.conkeror/1998/focus=1999|newsgroup discussion]]