Wait, what? How do I do that?
I can't go there due to the work filter, but go to the Gamefaqs MGS4 board and see if you see something about DLC or servers. It should be on the first page, and the thread has four pages IIRC. In there you will find the settings you need for your PS3.
When you do a connection test, it won't work. But turn the game on anyway, and it will allow you to DL them.