Configuring preferences and options in Outlook.com
I see. Thank you for clarifying, and I am sorry for the misunderstanding.
Please try the following steps if you are using the Navigation panel or bar of Outlook 365.
Click File > Options > select Advanced on the left pane > Check the Show Apps in Outlook box, and click OK > It will prompt you to restart your Outlook or close and reopen Outlook to apply the changes.
If you require further assistance, please don't hesitate to let me know.