See if your pet store has the book, The General Care and Maintenance of Red-Eared Sliders by Phillipe de Vosjoli. Sometimes it's sold under just the title of "Red-eared Slider" - just look for de Vosjoli's name on a slider book. It's a good book for starting with aquatics. This is also a good webstie: http://www.chelonia.org/Articles/trachemyscare.htm
These are considered aquatic turtles - they spend most of the time in the water, but need a place to "haul out" and bask. I like floating cork bark for this. Adult females will need a land area to lay eggs - they can lay infertile eggs even if never kept with a male. They also like a place to hide - so an underwater cave of sorts or artificial silk plants are a good idea.
Don't forget that these turtles grow to 6-12 inches as adults, and can grow to 6-8 inches in just a few short years!!!! Females really do best in ponds, and you can't determine gender until they are about 3-4 inches long.
As for food, many companies make turtle pellets, including Reptomin, Zoo Med, and Wardley's. They can also eat trout chow pellets, and Walkabout Farms makes a very high quality pellet (herpnutrition.com). They also eat dark leafy greens, aquatic plants, veggies, fish, earthworms, and insects.
Don't forget to investigate adoption before purchasing a slider. There are hundreds of sliders that need new homes. You could also try fostering to see if a slider is for you.
Katrina