See below the letter structure - you must fill all the fields marked.
Seller Name / Email / Phone number / address:
Those seller's information should be the same as the information of your Amazon seller central account.
*Seller details on support letter must match with the seller account details.
Brand Name (S): This is the brand name which you items will be exported with.
The brand name usually appear at the item's page.
Recommended: Using your own Amazon's store name as the brand name.
Brand Owner ( and Name/Title/Email/Phone Number) : this should be the same as the Seller information above.
Don't forget signing the letter and Date.
You can download the letter here