Separate my login id with default mail id

Separate my login id with default mail id

Hi,
I recently created a new account.  I created a new and default id (e.g. x@example.com).  Then as the process went along, it asked for a default e-m id.  I accidentally entered something different. (y@example.com)  I want to separate the two ID's as two separate mail accounts.  Can you please help me with it? 
I want the x and y to separate mail accounts all together.
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Thank you,
Nitin