In Explorer, you've got two buttons for spellchecking with the dialog, or with the Active Spell.
In Classic, you don't have the toolbar, so you can right-click within the clip, and access the spell checker that way.
There is also a Thesaurus, if you've installed it. Right-click on a word in the text editor, and you can access it from there.
Complete information on configuring the spellchecker, installing dictionaries and the Thesaurus, is here.