On this help page:
https://support.microsoft.com/en-us/kb/2431699... They advise you can use the "Skip" button to start using your phone. However, it won't have your Microsoft Account active at this time.
Use the "Contact Us" button at the top of the page to start a conversation with Microsoft Assistance about getting your activation code.
When the code is supplied, you can use Step #2 from the page I linked to return to the Activation screen and complete the process.
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