What does Oberon have Puck do about the two young men?

In Shakespeare's "A Midsummer Night's Dream," Oberon instructs Puck to use a magical flower's juice to make one of the young men, Demetrius, fall in love with Helena. Puck is tasked with ensuring that Demetrius, who currently loves Hermia, becomes infatuated with Helena instead. Oberon hopes to resolve the love confusion among the young lovers by manipulating their affections through this enchantment.