Your Office 365 email account has your personal authentication methods setup which are usually your phone number and/or personal email account. This is used for two-factor login and resetting your password.
If you need to change or add a method.
- Sign in to office.com
- Click on your account name in the top right corner.
- On the drop down choose view account
- A new tab opens
- On the left side of the new tab click on Security info
- When the page refreshes you can see the list of configured devices.
- This is where you can Change, Delete or Add devices
For more details Microsoft has a document here.