cd drive is missing from the My Computer folder help!

I placed a new DVD drive in my computer case without removing my old CD drive & now the Cd drive is missing. I know that one drive should be master & the other slave.
-but which one should be the master & which one the slave?
-how do i do it? how do I make a drive Master & the other Slave?(which cable for which drive)
-and what is "jumper"????