There is no magic button for female ejculation. It's really just a girl pissing on you (Though that's a bit of a simplification.). That "little round spot" is generally known as the "g-spot"; it's just the inner extension of the clit.
There's only one spot I've found that does it. The spot has always been successful at prompting an orgasm, but some ladies are just more prone to squirting, and some girls are embarrassed by it and will outright deny they can even squirt.
My gf can only squirt when she's on her back, I don't know why, and neither does she.... lol
In my experience using two fingers (I use ring and middle fingers, and point my index and pinky fingers down, running along her ass cheeks) and using an up/down movement, as opposed to an in/out movement does the trick. Don't move your fingers, keep them rigid and press down with the backs of your fingers towards her ass, and then pull up and flatten your fingers into her g-spot.
Shit works.... lol