There are a few parking options that are just down the block from the cruise terminal. SP + Parking (2 Bay St. or 1282 The Embarcadero) is relatively easy because there's a website for you to make an appointment and such.
I will say for the record, taking BART into SF and grabbing an Uber is easier and will give you a better peace of mind. There are a lot of smash and grabs all over SF whether it's street parking or a garage. Do not leave ANYTHING out.