If you previously purchased the software, you can still install it using your original media or by contacting Adobe Support for a direct download link.
If you don't have a license and want a free or low-cost alternative, consider these options: photoshop-download-cs6-free-windows-7-hot
Adobe originally offered a 7-day free trial for CS6, but they have since moved to a subscription-based model via Creative Cloud. If you previously purchased the software, you can
Downloading Photoshop CS6 for Windows 7: What You Need to Know If you previously purchased the software