Log in to Taobao and Douyin platforms, and enter the store or product details page where you want to add products.

Click the "Seller Center" or "Showcase Management" button to enter the showcase management page.

On the showcase management page, click the "Add Product" button.

In the pop-up window, select the Taobao product you want to add and fill in the relevant information, such as product name, price, inventory, etc.

After confirming that the filling is correct, click the "Save" button to complete the addition.

Synchronize the added Taobao products to Douyin's showcase. Enter the Douyin merchant backend, find "My Products", select the product you want to update synchronously, click "Modify", and then select the synchronized update option to complete the synchronized update.