1. First, determine the local postal system. Postal systems in different countries have different postal code formats and regulations. Before filling in the personal postal code, you need to confirm the local postal system and understand the relevant regulations.

2. Secondly, according to the local postal system and regulations, get the correct personal postal code.

3. Finally, when filling in the mailing address, there will be a special column to fill in the personal postal code, and fill in the correct personal postal code in the corresponding column.