Have a look at this part of the help center: I accidentally created two accounts; how do I merge them? It explains what you should to do merge two accounts.

See also:

• How can one link / merge / combine / associate two accounts / users? (Anonymous / unregistered / cookie, or Google / Facebook / registered) (Meta Stack Exchange)
• How do I combine my two accounts? (Meta MathOverflow)
• How can I unify/merge two of my accounts? ([Mathematics Meta]

Have a look at this part of the help center: I accidentally created two accounts; how do I merge them? It explains what you should to do merge two accounts.

See also:

• How can one link / merge / combine / associate two accounts / users? (Anonymous / unregistered / cookie, or Google / Facebook / registered) (Meta Stack Exchange)
• How do I combine my two accounts? (Meta MathOverflow)
• Announcement: New User Merge Policy/Tool (Mathematics Meta)
• How can I unify/merge two of my accounts? (Mathematics Meta)