Telling whether you have a Male or Female African Dwarf Frog:
Male: Smaller than the Female, has white/pink bump under armpits. "Sings" when it's hot outside and when it's trying to find a mate.  The male's abdomen has more of a U shape to it!

Female: Has a bump between legs. And has no bump under armpits.  The female's abdomen has more of a V shape to it!  Also, the female has a bigger body so she can hold eggs.
Picture
Female African Dwarf Frog
Picture
Male African Dwarf Frog