1st it has to be on California's approved list of handguns.
2nd it must only be shipped with 10 round magazines not the 12/13 rounders that were standard. Can of course be shipped with no magazines as well if it meets the 1st criteria above.
3rd it must be shipped to a receiving California FFL. (Federal firearms licensee). These can be gun shops, some pawn stores etc.
If all these are met you pay a fee to the shop who receives it for you. Do your background check. Follow any waiting periods that apply and then you take home.
Please note I am not a lawyer or California resident so the above is to the best of my knowledge. Just contact a local FFL and run it by them.