Make sure your computer or mobile device is first linked to the extender's WiFi network. Once you're linked up, open a web browser and type in the extender's default IP address, commonly "192.168.10.1" in the address bar. Press Enter to access the Wavlink AC1200 setup page. Usernames and passwords are required here. Enter "admin" as the password if the credentials have not changed previously. You can proceed by clicking the Login or Submit buttons. Upon successful authentication, you will be redirected to the extender's web-based setup page. From there, you can customize various settings, including network names, security options, and more. Make the desired changes and save the settings. Create a strong password for your extender, just to be safe. On the setup page, go to the administration or security settings area to do this action. After completing these steps, you will have successfully signed into your Wavlink extender and customized it to your specifications.