spread the lips, and lick from bottom to top several times. The clit will soon pop out from under the hood, but that doesn't mean stop licking!

as for size, I seriously doubt it would matter for sex drive...clit size would never come into play if a woman is disinterested in sex, and if the woman is seriously aroused and horny then the clit isn't technically necessary to do so, right?

and from my own personal experience, the clit will swell with arousal, just like a penis. although it usually doesn't get that big...might get up to twice its size (think a baby carrot, with most of it hidden under the hood)