The following instructions are for users on the Genesis Framework, using the Slider Pro plugin.
First, navigate to Slider Pro > Sliders from your sidebar
You should have only one slider in here, locate it and click 'edit'
From the edit screen, over on the right hand side, first make sure that Shuffle is unchecked
Once that's done, along the right hand side, locate Slides Order and click that
From here, you'll be able to rearrange the order of your Slider images. Make sure to click the blue Submit button when you're done making changes!