If you set up a revolution slider, there’s an option in the settings to allow a static layer, i.e. a layer that stays fixed on all the slides. Try creating a new slider, in general settings Enable Static Layers, then edit slides, you should see a Static / Global Layers tab on top of the settings, on the left. There you should be able to set a static layer. Try and set one, test if it works for you. I can’t make it work, could be some conflict between the theme and the plugin.