I really need help. I have 4 frogs the size no bigger then a fingernail. The are a blacky colour with browny/golden patches. I know they're carnivores now, but I don't know what to feed them! What is the smallest insect there is cause I really need to feed them something the size of a pimple! So please, what can I feed them?

Likely bugs and insects, look like these:
spring peeper (http://www.fcps.edu/islandcreekes/ecology/spring_peeper.htm)

U could try giving them ants or maybe that won't be enough protein so maybe green flys or miniture beetles its up to you what you give them but I can't think of any more insects which are suitable for your frogs.

Maybe you could put some food down that attracts bugs/insects, He can go from there.