Hey guys!
Currently adding your email via warframe.com is not enabled at this time. In order to claim the Synkra Syandana follow these steps IN-GAME:
1. Go to Options > Account (new tab on the far right) > Add Email
2. Check your email for a confirmation link from Warframe.
3. Confirm your email and you'll find the Synkra Syandana in your inventory the next time you log in!