Now that you have sorted out the correct ID, to answer the question about feeding and general husbandry;
I too thoroughly recommend the Pelusios.com Website, which covers all of the African side neck turtles, from Pelomedusa, and Pelusios Genus.
However, for general husbandry, these should be kept in tropical water conditions at 26 degrees centigrade, obviously Hygene, as with all Turtles is important, so Filtration is essential, ideally with an external canister filter.
The Turtles are very omnivorous in their diet and will eat a wide variety, of fish, molluscs, pellets, and green stuff. Aquatic plants such as Duckweed is taken with relish.
These Turtles are voracious feeders and are prone too over eating in captivity, so do watch out for obesity. This one looks quite young and has quite a bit of growing too do, but I would recommend feeding say four days out of seven, to avoid it becoming overweight.
In nature, they are used to spending periods of dry weather buried in the mud, when often their pools or ponds dry out completly.
I have kept a group of Helmeted Turtles for nearly twenty years and their character and habit is really fascinating. Because of their adult size and good temperament, I consider them a very good choice for the home aquarium set up. Whilst their not as colourful as the north American Sliders, Cooters, or Map turtles, they do have very endearing personality, and the permanent grin should keep the carer, happy for years.