Open the To Do app
§ On the left margin of the Outlook window, click the 
To Do icon.
Make the To Do app your preferred tasks management experience
You now have the option to specify your preferred experience for managing tasks in Outlook for Windows. There are a few different ways to configure this option.
§ On the teaching callout, click Try it:
§ In Tasks, click Try it on the yellow bar:
§ Navigate to File > Options > Tasks, then select Open tasks in the To Do app. You can switch back to Outlook tasks at any time by unchecking the setting.
How it works
When you select the option to open tasks in To Do, the following changes are made:
§ The tasks icon (
) is unpinned from the navigation bar (on the left margin of the Outlook window) and moved under 
More apps on the navigation bar. The To Do app icon remains pinned and visible.
§ When you select New Items > 
Task, it opens the To Do app instead of the classic Outlook Tasks app.
When you Open a task from the To Do bar, the Reminders window, or the Daily task list on the Calendar, it opens the task in the To Do app.
Open the To Do app on Web Version of Outlook
On the left margin of the Outlook window, click the To Do icon.
The To Do app looks like this:
