After you find your cabin and settle in a little, go exploring. Then there will be a muster drill around 3:00. Allow plenty of time to get back to your cabin, pick up your life vest and go to your muster station.
Then, after all the formalities, head to the Terrace, all the way aft on Lido Deck (14); get a bite at the Horizon Court buffet, a fancy rum drink at the the Outrigger Bar, and watch the sailaway. This is the best place to be; you get a great panoramic view of L.A. and Long Beach harbors. Once past the breakwater you can freshen up and get ready for a great dinner and a fun night.
Have a great cruise.