Microsoft 365 First Time Login
The first time you login, Microsoft will ask you to provide your mobile phone for SMS verification. Please complete the setup ASAP, otherwise, your mailbox login may be suspended.
Open your browser and go to https://outlook.office.com, please refer to the following screenshots for reference.
Enter your new email address
Enter the password
Click Next to continue
Please provide your mobile number for verification
You may click Yes here to save your login credentials, so it won't ask you to login next time when using the same browser.
Done