The steps to fill in the email address when opening a product showcase are as follows:

Open the Douyin APP and click on the "Me" icon in the lower right corner of the bottom navigation bar to enter the personal homepage.

On the personal homepage, click on the "three horizontal lines" icon in the upper right corner to open the side menu.

In the side menu, click on the "Product Showcase" option.

If the product showcase function has not been activated, you must first meet the conditions stipulated by the Douyin platform before you can activate the product showcase. For specific conditions, please refer to the official instructions of Douyin.

After meeting the conditions and successfully activating the product showcase function, you can see the "Email" option on the product showcase page. Click the input box and enter the email address.

After filling in the email address, click the "Save" button in the upper right corner to save the filled email address.