Amazon's "Deal of the Day" (abbreviated as "DOTD") is a daily special offer launched by Amazon. Merchants can apply to list their products as "Deal of the Day".

Here are the steps to sign up for Amazon DOTD:

1. Log in to Amazon Seller Center, find the "Promotion" option on the homepage, and enter the "Create Promotion" page.

2. On the "Create Promotion" page, select the "Daily Special (DOTD)" option and fill in the product information, including the product's ASIN code, promotion price, promotion time and other information.

3. Click the "Submit" button and wait for Amazon to review.

4. If the review is passed, Amazon will list your product as "Deal of the Day" within the specified time and promote it on the Amazon website.

It should be noted that the review of Amazon DOTD activities is relatively strict, and merchants need to ensure that their products meet Amazon's requirements and standards. At the same time, merchants can formulate reasonable promotion strategies according to their own sales strategies and market demand to increase product sales and popularity.