Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
As Placouk said, Office is NOT part of Windows. You have to buy it separately. Most new computers come with a "free trial" of 365 installed at the factory (MS pays builders to do that). Some, a very few, builders include a "free" 1 year subscription to 365 Personal, or even a "free" one-time payment Office license.
You have to buy a copy of Office 2021 (formerly 2019), or rent an Office 365 subscription.
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Talk to your family and friends to see if any of them have an Office 365 Family subscription which they have 1 of 5 unused "Shares" they can give you. Or someone who has 365 Personal and is willing to split the cost of "upgrading" to 365 Family. Even just 2 people sharing cost of 365 Family is cheaper than each paying for 365 Personal.
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Talk to family / friends who use MS Office at work. They may be able to get a 30% discount on 365 through the "HUP", Home Use Program.
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Which to buy depends on your specific situation and needs:
- If you have only one computer and don't need any of the fancy new "online"/"AI" features then 2021 will be cheaper in the long term
- If you have more than one computer, or need the new features, then 365 is your only choice.