To disable the slider. Go to admin -> appearance -> theme options -> homepage, then where it says Enable Homepage Slider, click Disable.
To enable a static picture, you can go to admin -> appearance -> Header, then where it says Select Image, follow the instructions and click Choose File, then upload. This will place an image above the navigation.
If you want just one picture where the slider should be, have you just tried uploading one picture to the slider? Not sure if it will work, but that’s all the advice I can give. ??