If you're just changing the display name of the extension, on older series (308, 616, 824) it is under "Names" in the ADMIN programming. On the CICS/MICS series, it is under "Terminals&Sets" under CONFIG programming. You must have authorization to get into these areas of programming and you must be at a M7310/M7324/T7316 console to access programming.
John Panzer