The following is a general method to set the bottom navigation bar on the mobile Taobao store homepage:

1. Log in to the Taobao seller backend: Use your seller account to log in to the Taobao seller center.

2. Enter the store decoration page: Find the "store decoration" option in the seller backend and click to enter the store decoration page.

3. Select mobile store decoration: On the store decoration page, select mobile store decoration.

4. Find the bottom navigation bar setting area: On the mobile store decoration page, find the setting area related to the bottom navigation bar.

5. Add a navigation column: Click the "Add navigation column" button and enter the name of the navigation column, such as "Home", "Product Category", "New Products", "Contact Us", etc.

6. Link settings: Set corresponding links for each navigation column, which can be pages in the store, product category pages, custom pages, etc.

7. Sorting and adjustment: You can sort and adjust the order of the navigation columns according to your needs.

8. Save settings: After completing the settings of the navigation columns, click the Save button to make the settings effective.

It should be noted that the interface and functions of Taobao may change over time and version updates, and the specific operation steps may be slightly different. If you encounter problems during the setting process, you can also refer to Taobao's Help Center or contact Taobao customer service for more detailed and accurate guidance.