First -- how largeare you turtles? They may still be too small to produce. Next if they did indeed mate you really don't have to worry too much. You just need to have a basking area for them that would allow the female to be able to dig a nest to lay her eggs. There are various sites that you can find specific information regarding this but there is really nothing to worry over as long as she has a nesting site for the time that she may decide to haul out of the water and lay.
I have had many sliders (that come through my rescue) laying eggs right the water of the quarantine enclosures. These eggs are generally no good if they are left in the water too long. Which is just as well. I get so many sliders through the rescue that the last thing I need to be doing is incubating and hatching more.
Just run a general search like (breeding sliders) and I am sure you will get a bunch of info. and can find something that will suit your situation.
Steve