Right now, PlayStation 4 owners can download the Dark Souls III stress test client. The servers don't appear to be up right now, but you should probably get the client downloaded for when the servers do go live. I am assuming that this test will take place this weekend only.
Until such a time, you should probably listen to the main menu music, it's pretty great.
Until such a time, you should probably listen to the main menu music, it's pretty great.