Your question is answered on our big parent Meta site, Meta Stack Overflow: 

> ### [How can one link/merge/combine/associate two accounts/users? (Anonymous/unregistered/cookie or OpenID/registered)](https://meta.stackexchange.com/questions/18232/how-can-one-link-merge-combine-associate-two-accounts-users-anonymous-unregist)
> 
> […] follow this procedure:
> 
> Set the email address of your registered account to the address used
> in your other account. Since email is not visible to anyone, this will
> confirm that you own both accounts.
> 
> Edit: Some people have had trouble with this step. If you have two
> registered accounts and cannot make the email addresses the same, an
> alternative option is to make a note in one of the profiles: "Please
> merge this account into <link to other account>."
> 
> Flag one of your posts for moderator attention and ask for a merge.
> 
> If the details match, we will go ahead and merge with no further ado.
> If we feel we need more confirmation for some reason, we will either
> comment or email to tell you.