At the beginning of your upkeep, discard a card at random. If you discard a creature card this way, return it from your graveyard to the battlefield unless any player pays 5 life.
First, the card is discarded. Then, in turn order, each player is given the option to pay 5 life. Then, if no player paid 5 life, the card is put onto the battlefield from the graveyard.
The card is actually discard, so anything which triggers on a discard will trigger. Such abilities will wait to go on the stack until after this ability has completely resolved.