How to set the extension in Asterisk?

How to set the extension in Asterisk?

Hi SCP Suppport
    How to set the extension number in Asterisk? The extension is assigned to support Rep. If I set in asterisk->extension, there need define a password for this extension,but in SCP, there is no place can input the password when I enable the support Rep call alert pop-up function! 
    Thanks!
 
From looklee 

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