What do I do with a Common Garden frog?

This morning I stepped out to find my two cats taunting this frog. After scaring them of, I picked it up, thinking it was dead. However it seems to be fine. I've put it in a large plastic container with bottled water a leaf, stone and gardening spade (for protection) and covered it with a tea towel and put in part shade part sun. But really I have no idea what I'm doing. I have a small garden and no pond, I'm scared to let it out because my cats are still around. What should I do?