WhenWorks integrates with Outlook.com through the built-in Calendar app on iOS. Therefore, in order for WhenWorks to access your Outlook.com calendars, you must configure the Calendar app on iOS to sync with that service.
Here is how to configure Outlook.com syncing on your iOS device.
Open the Settings app and tap Accounts & Passwords > Accounts > Add Account > Outlook.com. Then enter your login details.
On the next screen make sure that Calendars is enabled.
Once your iOS device is syncing with Outlook.com, WhenWorks will be able to access your real-time availability and add appointments to your Outlook.com calendar.
If there are read-only calendars on your Outlook.com account, like Birthdays and Holiday calendars, you should disable them from affecting your availability. You can do that by opening WhenWorks and tapping Settings > Calendars Affecting Availability.