Hi Mom,
Here's a link with some info on turtle feeding. In fact, you might go ahead and read up on the whole subject under "nuitrition". It's very helpful.
http://www.redearslider.com/pellets.html
Turtles can't swallow unless they are in water, so all their food should be put in the water. If you give them more than they can eat so that some is left over, it will quickly spoil in the water, so the leftovers should be removed after he's finished eating.
Alternatively, a lot of people will remove the turtle from the tank and feed him/her in a separate container - like a big bowl or tub. That helps keep the tank water clean. A lot of turtles will poop right after eating, so if you let them take care of that in the separate container, it will help even more with keeping the tank water clean.
Whether feeding outside the container works or not depends on the turtle. If yours is very little and you haven't had him long, then he's probably too nervous to be removed from his aquarium (the only safe place he knows!) for feeding. When he seems more confident, then you might try out-of-the- container feeding. Until then, just be sure to remove any uneaten food from the tank.
It's hard to resist over feeding the little turtles because, once they get to know you, they get real exciting about being fed and it's soooooo cute. Be sure and follow the directions closely on the amount to feed because either over feeding or under feeding is bad for the turtle.
On how to tell their sex, you won't be able to tell until they are at least 4" long. Then, it suddenly becomes quite obvious! Here's some info on the subject:
http://www.redearslider.com/determining_sex.html
