When you first start Microsoft Outlook, you will need to add an account. Follow the steps to add an Outlook.com or Microsoft 365 email account. After you've finished, you can add more accounts.
Type in your email address, then select Connect.
Type in your password and select OK.
If you want to add an additional account, select File > Add Account and repeat the steps.
Note: Some email providers, like Gmail, Yahoo, and iCloud, require you to turn on two-factor authentication and set up an app password. See Add an email account to Outlook for more information.