Both in-store and online purchases are eligible.
Deal should show up in the offers page under "My Account"
OFFER TERMS: Limit 1 statement credit per American Express Card across all American Express offer channels. Statement credit will appear on your billing statement within 8 weeks after American Express receives information from the merchant about your qualifying purchase. Note that American Express may not receive information about your qualifying purchase from the merchant until all of the items from your qualifying purchase have been provided or shipped by the merchant. Statement credit may be reversed if qualifying purchase is returned/cancelled. If American Express does not receive information that identifies your transaction as qualifying for the offer, you will not receive the statement credit. For example, your transaction will not qualify if: (i) the merchant uses a mobile or wireless card reader to process it; (ii) it is made with an electronic wallet or through a third party; or (iii) it is not made directly with the merchant.