Red eared slider turtle baby care

Question
Well I was in a small mom and pop kinda store and saw these
little turtles, i thought they were cute, I bought a small
tank with two turtles in it, and got the advice from the
owners oh there no trouble just keep the tank clean and feed
them and they'll be fine. I thought well if this store is
keeping them and they look fine they should be easy... then
I went to a real pet store and found out the the were sold
to me illegally, because there about an inch may be longer.
but i figured well now that I have them I might as well give
it my best to help them thrive. I bought them a 10 galleon
tank got a "dock" for basking, and a thermometer. I also
bought a different kind of food because the stuff that came
with them seemed to big and I think it was beta fish food.
My question is I've had them for 3 days now and one of them
doesn't seem interested in eating, i even gave it the old
food. now he may be eating at night but if he is its not
much. what other things can i try? I want to try my hardest
to do right by these little guys but theres not much info on  
how to care for the really little ones? any help you can
provide would be greatly appreciated or at least point me
toward some good reliable info.  

Answer
Hello thank you for your question.
I will try to address each concern.
First however please let me remond you how important it is that you maintain clean hands, wash before and after handling the turtles.
You can get salmonella and you do not want this. Also spray your sink handle after use as well.

Now, the reason that they are not intrested is because they may still be living off the yolk from the egg. they can survive a short while without eating.

Did they tell you that you also need uvb light, you need filtration, and the future care involved?

So now, you need to be sure they get uvb to do this you have a few options. you can get a uvb bulb ( I prefer mercury vapor bulbs) this provides the turtle the ability to absorb foods, calcium vitamins etc it contributes to shell maintanence. IT IS MANDITORY. To get this you can also provide outside time  NOT IN THE TANK. Glass doesnt release heat and it will kill them.

Now if the temps are correct, then we move to feeding water and basking.
Water:
The water needs to be three times their body So if they are 1 inch then they get 3 inches of water. Provide an area on one side of the tank with the heat light habging over this is the basking area. the temps here will; be warmer than other areas. This also keeps the water in tank warm for them.
Also they need an area to get OUT of the water. This provides the ability to dry off preventing fungal growth.

feeding:
they will eat a standard turtle floating pellet. IN TIME they are not necessarily hungry at this time. as previously mentioned they are still absorbing the yolk. You can get shost shrimp at the pet store and try these.

Please let me know if I can be of further help.