If you want to change your work or school account password in Office 365 for business, it's a relatively simple task.
If you’ve forgotten your work or school account password or it’s no longer working, you can go to the self-service password reset tool to try to reset your password. If your admin hasn't enabled self-service password reset, use this tool to send a password request to your workplace technical support. This is typically the person with admin permissions who set up your Office 365work or school account for you. If you want to contact your workplace technical support team directly, send them a link to the admin help topic Reset a user's password.
If you're an admin for an Office 365 organization, and you've forgotten your password, check out Reset my administrator password for Office 365.
Change my work or school account password
Go to Settings > Office 365 settings > Password > Change password.
Type your old password, and then type a new password and confirm it.
Some users can’t change their password in Office 365 because their organization creates and maintains their accounts. If you don’t see a link to change your password on the Password page, you can’t change your work or school account password in Office 365. Your organization might have sent you instructions to help you change your password. Follow those instructions to change your password, or ask your admin for help.
Note: When you change your password for your work or school account, be sure to update the password on your phone and desktop email program to match the new password for your account.