Step 1: Go to Slider Revolution and hit the slider you want to edit.
Step 2: Choose Main/Background Image if you want to change it, then hit Media Library or Object Library depending on where you want to get your image.
Navigate to other tabs: General Settings, Thumbnail, Slide Animation, Link & Seo, Slide Info, Nav. Overwrite to customize. You just have to follow those comprehensive instructions.
Click Save Changes after you finished the customization