For all themes, Swite allows you to customize the cover picture, is the largest photo at the top of every page of the site. To add or change it, follow the indicated procedure:
• From the navigation bar, click on Site Editor
• Than on Sections, if it's not there already, display the section Cover
From here you can chosse between:
1. Upload a picture from your device.
2. Get the picture from your Social cover connected
3. Use a default picture
Then just click on Save to confirm your changes.