hold or host

(もよおす) To host a small event – a party, for instance. Unlike 主催、 催す has the idea that you’re responsible for what happens, rather than just giving money to the event.
(しゅさい) To sponsor a large event. “This golf tournament is brought to you by Penzoil.”
(かいさい) To open a huge event. The opening ceremonies. “Is that expo open yet?”