You can't. CS6 is too old for your modern Mac machine.
If you have installation disks for the Windows version of CS6, you could install on a Windows PC or Windows running on a virtual machine. But without a Windows version of the software, you're totally stuck. Sorry.
Photoshop Elements and Premiere Elements ($ave 25% until January 3, no subscription needed).
https://www.adobe.com/products/photoshop-elements.html
Premium Adobe Express ($10/month).
- Adobe Express app (web and mobile)
- Premiere Rush (video editor for desktop and mobile)
- Photoshop Express (mobile)
- Spark Video (mobile)
- Spark Page (mobile)
- Adobe Portfolio + hosting
- 100 GB of cloud storage
- All premium templates and design assets including the collection of over 160 million royalty-free Adobe Stock photo collection.
https://helpx.adobe.com/express/using/express-overview.html
Creative Cloud All Apps (51 + pro apps & services). Single App Plans also available.
https://www.adobe.com/creativecloud/plans.html
Hope that helps.