The steps to set up 7-day unconditional return on Taobao are as follows:

1. **Download and log in to Qianniu client**: First, you need to download the computer version of "Qianniu" client and log in to your merchant account.

2. **Visit Taobao service**: In the operation background of Qianniu, move the mouse to the "Taobao service" section.

3. **Join the service**: Click "Join the service" to manage.

4. **Select return commitment**: In the management interface of "Join the service", find the "Return commitment" option and click it to join the seven-day unconditional return service.

5. **Set up store service**: Generally, the settings of the store need to be set in the seller center of the store background. In Taobao service, you can find the service product management option and make relevant settings.

6. **Self-check the qualifications for selecting return commitment**: If you want to set up a no-reason return period of more than 7 days, you can find the relevant options in the service product management and conduct a self-check of qualifications to ensure that your store meets the conditions for joining this service.

7. **Operate according to requirements**: If the store meets the conditions, follow the prompts to join the service.

8. **Detailed rule settings**: After the settings are completed, you need to set the detailed service content of the product according to Taobao's requirements, such as return cycle, postage, etc.

Please note that Taobao stipulates that certain categories of goods must join the "7-day no-reason return" service, regardless of whether the seller is willing to join. When returning goods in these categories, buyers need to ensure that the goods remain intact and return all related accessories.

The above steps are based on a summary of online resources, and the specific situation may change. It is recommended to read Taobao's latest rules and guidelines carefully when operating.