Short answer
HubSpot's KB: from a meeting in Outlook calendar, use the Office 365 add-in to prepare, follow up, and set outcome, type and associations, such as the contact's company or deal. Prep and follow-up need Sales Hub Professional or Enterprise.
1. In HubSpot
The relevant screen in my demo portal.

2. Worth knowing
Calendar sync must be connected for meetings to log.
3. Related
Calendar sync and add-in sales tools.