Wild Baby Yellow Bellied Slider?

[Dogs are awesome]

I found this baby slider and it is like REALLY tiny. Only an inch I would say. I do not want him as a pet, but I found him far from water near my garage. It is pretty late also I would not be able to release him due to the lack of place to release. I plan to release him though as soon as I find a lake, river, or nice pond somewhere. We are in central florida and it is pretty cold at the 50s. I do not know how to care for a turtle, I am more use to lizards. Right now, he is in a big container filled with water that is room temperature. He has a little floaty thing I made out of this soft paper that thing that is hard to explain. It is foam paper, but not the kind that flakes. I put sand on that from where I got him, and the vet told me to put lettuce in his cage, which I did. His container has a heater under it to keep the temperature nice.

I keep on reading things on the web, but I'm so nervous that he might die due to my lack of knowledge.

So, how do I release him? when do I release him? how do I care for him in the mean time? Is it to cold to let him out?

Thanks!
And that reason was probably my dogs