Omaha Hi/Lo is played the same as Omaha, with two exceptions.
One, that the game is played as High/Low. After the betting round following the River, the pot is split between the player with the highest hand at the table, and the player with the lowest hand at the table. The dealer or House will need to determine if "Hi" and "Lo" needs to be declared in clockwise order before showdown (or if 'cards speak'), and if a player is permitted to call "Both" using different five-card combinations of his or her nine cards.
Two, that in order to win 'Lo', a player must have no higher than an 8-down. If no player has an 8-down or less, then the game is played as All-High.