You can add the phone number after the WeChat nickname, that's all.
1. Open the mobile phone WeChat and click me.
2. On my page, click on the avatar.
3. In the personal information page, click on the name.
4. Add your phone number after the nickname, and then click Save.
In this way, you can add your mobile phone number to your WeChat nickname, and others can directly see your mobile phone number.