How do I open/launch and encrypted dvd?

I have received a dvd that I need to open. I have been sent the encryption code/key via mail. When I insert the disk into my MacBook Pro, the disk spins and whirs; but, it never shows up in Finder or on my desktop. It just eventually ejects itself. How do I get to a point where I can enter the encryption key/pass code to view the contents of the disk as intended? Thanks in advance.