There are others here that are more experienced at this than I am but here goes...

Choose a celebrity you would like an autograph from. Find their address in the database, write them a letter requesting an autograph (tell them why you like them, etc.) enclose a photograph that you would like signed, also send a self addressed stamped envelope for the return. Mail it and wait.
Some celebrities charge for an autograph but many don't.

Good Luck.

hello i am new here and do not know how this works right. I live in Brazil and do not know how to ask. some help please? have to pay? how do I order by mail? Thanks to those who help