How can I enable Key Repeat on my MacBook Pro?

hi - there are times when i like to hold a single key down on my keyboard to repeat the letter. but on my new macbook pro (13 inch, late 2011), it won't let me do that. and i've looked at system preferences and set all the settings to where i would think i could repeat letter by holding down a key. I even tried the terminal thing but it didn't work (in apple developer if that help

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