How do I order the mattress online?

I want to order the mattress online because I don't have a car and I heard that buying one from store and have them deliver to me is really expensive. So I want to order it on Amazon.com. Problem is, how do I receive it? I've been ordering from Amazon in like 2-3 years but I never order something like bed mattress before... Right now I'm moving into new apartment, my apartment is in Santa Monica, California, US with no furnished room. My apartment building has gate community. How does the mailman deliver my mattress? will he deliver it to the landlord if I'm not home? will he just left it in front of my door? If possible please give the advise on how to do it. Or best way to get the mattress the cheapest and easiest as I can. P.S. I am foreign college student