Hi Khalid. This is from a search I did...
Go into icloud mail [icloud.com] and select preferences in settings on the left sidebar at the bottom. Select "Accounts" which will list your @me.com and @icloud.com aliases. The @me.com cannot be changed, but you can create a new alias of the email address you would prefer. This address will be an @icloud.com address.
Then go to "composing" tab. Set default address to the new alias you created. Then below that, deselect all the other email accounts and select the new alias.
This doesn't get rid of the @me.com email, but when sending mail, it will at least use your preferred address sending and receiving. Occaisionally the @me.com will pop up, but for the most part you can just forget about that address and use your new icloud alias.
There's also this, but it's from 2011 so it might not work...
Go to me.com you will find a blurb there to click on to move from mm to icloud. follow oncscreen prompts. If you type http://me.com/move
it will take you the same screen too.