The lead time on the AliExpress platform refers to the time period from when the seller receives the order to when the goods are shipped. If you need to set the lead time to 8 days, here are the general steps:

1. Log in to the AliExpress seller backend.

2. Find the "Product Management" or "Commodity Management" related options on the backend page.

3. Select the product you want to set the lead time for.

4. Click "Edit Product" or "Commodity Details" to enter the product editing page.

5. Find the setting options for "Lead Time" or "Shipping Time" on the product editing page.

6. Select the "Lead Time" option and enter "8" days as the lead time.

Please note that the following are some details that may need to be paid attention to:

- Different categories of goods may have different lead time limits. Make sure that the lead time you set complies with the regulations of the AliExpress platform for that category of goods.

- In special circumstances, such as holidays or promotional activities, the platform may adjust the rules for the lead time. Please pay attention to the platform's announcements and set them according to the latest regulations.

- If you are using an overseas warehouse to ship, the lead time settings may be different and need to be set according to the specific regulations of the overseas warehouse.

- When setting the lead time, you must also consider the actual situation of the goods and the supply chain capabilities to ensure that the shipment can be completed within the promised time.

If you encounter difficulties during the setting process, or the steps are different, you can refer to the latest help documents of the AliExpress platform, or contact AliExpress's customer service for help.