Using New Outlook on Windows for professional communication and productivity
Where did you see those instructions? That location for editor options is outdated - and I don't recall seeing autocorrect as an option in new Outlook. When I checked the roadmap, autocorrect found nothing but there are options for spell check. I would add the name to the personal dictionary - if it's not already there, to might be offered as a predicted test.
Open a new message. You should have an Editor button on the ribbon (options tab) or click on the icon in the lower right - either opens the editor settings. Scroll to the end to access the options. But I don't see a way to edit autocorrect from the settings.
The ribbon button includes the personal dictionary - but that underlines bad spelling, not autocorrects.