It was setup as standard.
Go to Admin -> Posts and Topics -> Post Settings. Then make sure the box marked
Enable spell checking is checked. If I click on the question mark next to this box I get the following message:
"Enable spell checking. You MUST have the pspell library installed on your server and your PHP configuration set up to use the pspell library. Your server DOES appear to have this set up."
If you don't have the pspell library installed on your server you should contact your hosting company.
Hope this helps.