Pick one of the Clarity Non-Production Upgrade Slots or Clarity Production Upgrade Slots that are suitable for you
Raise a case with Broadcom Support or Rego SAAS Support depending on your Primary Support contract and request the exact upgrade slots that work for you
Also provide exact environment URLs for this request
Raise a separate case per environment
The Support team will get back to you to confirm the scheduled date / time for the upgrade. In the rare occasions where the initial slot is no longer available, you may be asked to provide an alternative