Go to Settings > Calendar settings.

Click on the large orange "+" button at the bottom right of the screen to add a calendar.

A pop-up will launch to guide you through connecting with your calendar. If the pop-up does not appear, please check whether the pop-up is being blocked.

Select your calendar service and sign in with your credentials to proceed. 

You can connect multiple calendars and select the sub-calendars that contain meetings with customers.

Past meetings will start appearing in account timelines.

Future meetings appear in the Today and Upcoming Tasks lists.