Microsoft 365 login page -
https://login.microsoftonline.com - clicking the link you should see the following login-box.
school email address given to you by your learner/teacher or local servicedesk. It is also your Office 365-id
Enter your password and click "Sign in". Contact your local servicedesk if you have forgotten your password.
By selecting yes, your login and password (encrypted) are saved on your local computer.