rebekahstudio on "If I want to test a new theme, e.g. Vostok ..."

If I want to test a new theme, e.g. Vostok that doesn't display in the preview all of its stated features and variations, how do I do it without "erasing" my current theme and blogsite. I don't want to switch until I'm sure it will work for me. Are there some settings I need to know, or what? Or can someone point me to the instructions? Thank you for your help. Rebekah
http://rebekahstudio.wordpress.com