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Specify Amazon Key ID and Amazon Secret Key which you just obtained in the first 2 fields >> Save Changes.
Select Manage, choose an existing bucket or create a new bucket and Save.
Next go back to Settings, you will see all the fields are filled with proper information for you. Please do not change values in Bucket Region & Bucket Name.
Once you have filled out those settings you can click Yes for Enable CDN and Save Changes to save all settings.
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