If you're looking to change the email that you used to sign up with, you can do this by heading to settings > account details and clicking on change:
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You will be asked to verify your current email address:
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Once you have clicked Send Verification email this will change to Awaiting verification:
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You should receive an email as follows:
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Click on confirm my account and this will confirm if your email has been verified:
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Head back to Ember and you will be able to set a new email!