RES (Red eared slider) care, Based on pictures I am guessing he is 4-5" which means he would need a 50 gallon tank. You base the size of his housing on his length - basically 10 gallons for every inch. You will want a large tank, 55gal rubbermaid tub, kiddie pool, etc. Fill whatever habitat to the point that he will not climb out, probabley about 6" or so from the top (they will climb out if they get the chance, then good luck finding him). You want a good filter, it is the only way of keeping the smell gone, I personally have a 125 gal tank w/ 3 res inside, I use a fluval 405 canister filter and 2 internal cascades - they keep the tank clean but at first chance I am getting another one. Don't buy the cheap filters they sell for turtles or even the cheap ones for the back of the tank - they don't work, your tank will smell and constantly dirty. If you decide to start with a 55 gal tub - one fluval would work and you could put a drain in the bottom of the tub for easy cleaning.
For lights you will need a heat lamp and a uvb bulb, zoo med sells a water turtle heat lamp - which is suppose to be splash proof, I got one recently and have had no problems with it - my previous ones kept breaking do to the turtles.
You want to you large rocks for the bottom - make sure they are bigger then your turtles head that way he won't eat them. You could also put live plants in there but plan on them being pulled out or eaten frequently.
As for food, I use reptomin turtle pellets, I feed them those every other day, twice a month I buy 60 rosey red minnows or guppies and put them in the tank (for 3 RES & Fish), I give them a few red wigglers or earth worms every couple of days, Plus I give carrots, red leaf, green leaf, endive, escorele, romaine, dandelion greens, squashes, fruit, every other day. Mine do not eat a lot of the veggies and greens yet but they are starting to. (they were never given before I took them in). **Any extra food floating after 20-30 mins scoop out with a fish net otherwise your tank will become nasty. **A good ratio for feeding is Commercial food 25%, animal matter 25%, Plant matter 50%, vitamin supplements 2-3 times a week. I use the worms as the main protein, and the fish more as exercise, when the fish are in the tank don't give the worms. A few more caresheets are
http://www.austinsturtlepage.com/Care/ca...slider.htm and
http://www.anapsid.org/reslider.html, Good Luck and feel free to ask any other questions.. And welcome to TFO glad you found us!!