Spell Check As You Type (SCAYT) functionality is enabled by default in MindTouch.
SCAYT checks your document for misspellings as you type your text. SCAYT underlines any misspellings with a red line a few seconds after you type the word.
To correct the misspelled word, right-click the word and you'll be presented with options to select. Select the correct word to update the text.