The instructions for a firmware update can be found at: https://docs.extrahop.com/6.1/eh-admin-ui-guide/#update-to-a-new-firmware-version
It is usually a pretty painless process, but it is always a good idea to make a backup of your customizations first and download the latest support pack from your Extrahop.
A quick email to support to let them know you’re planning an upgrade and a rough time frame may also be a good idea. If there are multiple parties managing the Extrahop platform in your space then there is the possibility of a special configuration you may not be aware of that may require special upgrade procedures.
With respect to finding the available firmware, they’re all available to download at:
You will need a login to download them. The latest 6.0 version is 126.96.36.19915 and there is also a 6.1 release available now as well.
I hope that answers your questions.