The steps to upload authorization letters on Taobao are as follows:

1. **Log in to Taobao seller platform**: You need to open Taobao seller platform in the browser and log in with your seller account and password.

2. **Enter store management**: After successful login, click the "Seller Center" button in the upper right corner of the page, and then select "My Store" to enter the store management page.

3. **Find brand authorization**: On the store management page, find the "Brand Authorization" option in the left navigation bar and click to enter.

4. **Add a new authorization letter**: On the brand authorization page, find the "Add a new authorization letter" button and click it.

5. **Fill in the authorization letter information**: Fill in your authorization letter information as required, including brand name, authorization letter validity period, etc., and upload the scanned copy of the authorization letter to the system.

6. **Submit for review**: After filling in the authorization letter information and uploading the scanned copy, click the "Submit for review" button. Taobao will review the authorization letter you uploaded, which usually takes some time, please wait patiently.

7. **View the audit results**: After the audit is completed, you can view the audit results through the "Brand Authorization" page.

Please note that the authorization letter you uploaded is authentic and valid, and consistent with the brand of the goods you sell. If you have any questions or need further help, you can contact Taobao customer service for support.