The steps to install these versions can be different depending if you got Microsoft 365 through one of the following ways:

Some versions of Microsoft 365 such as Office Professional Plus 2021, Office Standard 2021, or a stand-alone app such as Word 2021 or Project 2021 don't have an associated Microsoft account, or work or school account. *If you don't have a product key or an account You'll sign in with your work or school account for these versions of Microsoft 365. Once you verify you have a license, anytime you need to install or reinstall Microsoft 365 you can go straight to the section below, Sign in to download Office and select the tab for steps to install on a PC or Mac. Learn how to check this in What Microsoft 365 business product or license do I have? or if you're a Microsoft 365 admin responsible for assigning licenses to people in your organization, see Assign licenses to users. If your Office for business subscription plan includes the desktop version of the Microsoft 365 apps you won't see an option to install it unless someone in your organization assigned a license to you.

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