1. Log in to the panel https://panel.callback24.io/ with your credentials.
2. Go to the Settings -> Services, click on your service or Add New and go to Advanced Settings.
3. Click on the arrow at the bottom of the Custom CSS page.
4. Enter the code to change the appearance of the pop-up. You can change the color, background, and font.
5. After filling in the field, select the Save button.