I bought clothes on Taobao for the first time. The seller said he would leave a message to determine the size. How to leave a message?

Before you confirm the payment of the order in advance, there will be a window asking you to confirm the delivery address and personal information, including a box "Leave a message for the seller". You can write down the necessary information in the message, such as "I took the L number, please change it to M when shipping". In this way, you can also contact the store directly and ask him to give you an explanation.