To refund a customer on AliExpress, you can follow the steps below:

1. Log in to the AliExpress Seller Center: Use your AliExpress seller account to log in to the AliExpress Seller Center.

2. Enter the order management: Find "Order Management" or similar options in the navigation bar of the Seller Center to enter the order management interface.

3. Find the order that needs to be refunded: In the order management interface, find the order that needs to be refunded. You can filter and search according to information such as order number and buyer ID.

4. Select the refund option: In the corresponding order, select the "Refund" option and fill in the refund amount and refund reason and other information according to the system instructions.

5. Submit a refund application: After confirming that the refund information is filled in correctly, submit a refund application. The system will process the refund request and notify the buyer.

Please note that the specific refund process and operation may change due to updates to the AliExpress platform, so it is recommended that you follow the instructions provided by the AliExpress Seller Center, or consult AliExpress customer service support to ensure the correct operation of the refund process.