Q: How do I upgrade from 10.6.8 to something newer as this wont support my new camera.

Go to the App store for upgrades

Well, we'd need to know the model/year of your Mac to see if it can be upgraded.

OS X El Capitan - Technical Specifications

Please note that the 2 GB mentioned will not allow you to do more than browse the internet and/or word processing. A minimum of 4 GB is generally recommended; more if you do video/graphics editing/rendering.

If your camera uses SD cards, you can simply take the card out of your camera and use a USB card reader on your Mac.

That depends on which iMac model you have....?

see > Identify the model of your iMac - Apple Support

Then check out > http://www.apple.com/osx/how-to-upgrade/?cid=wwa-us-kwg-mac to see if your model qualifies.