Spell checking in done in one of two ways: As-You-Type and/or using the Spell Check button.
By default As-You-Type option is turned on. This option will place a red wavy underline under each word not in the dictionary.
To correct each work right-click on it to open the popup menu with possible spelling changes.
You can also spell check the entire memo field by clicking on the Spell Check icon on the top toolbar.
This option will open a form to alert you to words not in the dictionary.