I am using an older version and would like to upgrade, but I don't see any documentation regarding upgrading
Thanks for reaching out to the community.
If you want to upgrade your Analytics license, the best way would be to reach out to the Analytics Account Manager for your company. They would take you through the upgradation process.
Some documentation around upgradation can be found here - https://marketing.adobe.com/resources/help/en_US/mcloud/upgrade-to-analytics-premium.html
Let me know if this is helpful. Thanks!