The Spelling Check can be evoked from the Text Side Bar (shortcut F7). The check will start in the current text section and move through the whole of the Text and Reference Panes, section by section, until complete. Like all spelling checkers, at first it will not recognise some proper names and abbreviated forms, and you will need to add these to your User Dictionary using the Add button on the spelling checker. If you already use a spelling checker for e.g. Word, you can specify its User Dictionary) as an external user dictionary for Audio Notetaker's spelling checker. To do this go to App Menu → System → Settingss → Spell Check, where you will also find other standard spell check parameters which you can set.
You can set Word to use Audio Notetaker's custom dictionary. Audio Notetaker's dictionary can be found in; C:\[User]\AppData\Roaming\NetSpell\user.dic