Hi jnonatti, to vote you simply click on the circle with an up arrow in it. If it's white then you can vote, but if it's blue then you already voted. And the whales are the high rollers here, they're the ones with the most steem power. Minnows are us, we're the ones who are just starting out and need more steem power so we can become bigger fish. All the whales, minnows, dolphins, etc... are fish metaphors based on the size of the fish to represent their steem power.