In order to view your company cases you will need to have access to your Private Support Group aka MyJive Group. If you have access to your companies MyJive Group, you can go to Get Help > MyJive Group. If you do not have access, you will need to be invited by your Community Manager.
If you do not know who your community manager is and you are hosted by Jive, please let me know the URL of the site. Or if you are an On-Prem customer, please provide your company name so I can see who it is.
This documents, discusses this a little more MyJive Secret Support Group Administration FAQ