Hi Curtis,

1. Ensure your DMAs meet the requirements : DataMiner Compute Requirements | DataMiner Docs.
2. After finalizing the version you want to upgrade to, you need to read this first : Preparing to upgrade a DataMiner Agent | DataMiner Docs. This extensive documentation mentions everything you need to know prior to upgrade (such as prerequisites, upgrade paths, backups, issues etc).
3. Ensure you take proper backups before upgrading. If you have VMs, VM snapshots would be ideal. The link in point 2 also mentions this.
4. Next, upload the upgrade package as in Upgrading a DataMiner Agent in System Center | DataMiner Docs. Always choose all agents in the cluster as in point 6 and if you have failover pairs, you need to choose upgrade main and backup agents simultaneously, as in point 8.
5. Finally, you execute the upgrade as per the above documentation.

I can't stress this enough, but reading Preparing to upgrade a DataMiner Agent | DataMiner Docs is extremely crucial before you upgrade!!

You can download packages from DataMiner server upgrade packages - DataMiner Dojo and here you can find the difference between main and feature release : DataMiner Main Release vs. Feature Release | DataMiner Docs

All the documentation is available under the heading Upgrading a DataMiner Agent | DataMiner Docs.