You can get the certification by studying the scrum guide (the free download from scrum.org) and then doing the PSM-I exam online.
I have only done PSM-I and PSD-I but for these two the scrum guide and the open assesments are enough, in fact the scrum course (no idea if it was scrum aliance or scrum.org or some independant, I dont remember) I did just added confusion by talking about extending scrum with sprint 0 and so on which was unhelpful.