Reveal the top five cards of your library and separate them into two piles. An opponent chooses one of those piles. Put that pile into your hand and the other into your graveyard.
If one of the piles is empty, the opponent will choose whether to put the cards from the other pile into your hand or into your graveyard.
Steam Augury doesn't target any opponent. In a multiplayer game, you choose the opponent as the spell resolves.