how to register the headset with the base unit?

I have southwestern bell cordless phone model GH3000AT >>at sudden the headset kept clicking while it was not on base and since that I cant reconnect it back with the base>>>and when i press the button "Talk" on headset it keeps flashing for many times and then it beeps and turn of back..no line in headset...Can you help me how to register my headset back to the base unite?tank you