Once you have purchased Office, you can install it from the Services & subscriptions section of your Microsoft Account page https://account.microsoft.com/account/Account
For further assistance with downloading, installing, reinstalling, or activating Office, and/or more guidance on Office updates, this article https://support.microsoft.com/en-us/office/download-and-install-or-reinstall-microsoft-365-or-office-2019-on-a-pc-or-mac-4414eaaf-0478-48be-9c42-23adc4716658 in Office Support.