The steps are as follows:

1. Confirm the qualification: Ensure that the catering store meets the requirements of the US delegation's take-out, including relevant licenses and certificates.

2. login to meituan merchant platform: log in to meituan merchant platform with meituan merchant account.

3. open the food preference button: find the global settings in the account center and enable the food preference function.

4. Submit the application and wait for approval: fill in the application form for preferred merchants, and wait for the approval of the US Mission after submitting the application. After the approval, you will get the logo of the preferred merchant.