As far as I know there are three ways to do this:
1. Create a new scene with only one step. Set your dimmer/red/green etc channels where you want them to fade to. Set "Fade state" to "fade" (little symbol under each channel). Adjust the time and save your scene.
Now add the light scene to your live screen. When you click on it your dimmer will fade up.
2. Add the scene to your live screen as you did it but right-click on it and select scene settings. Here you can set the loop on 1.
3. May be the easiest: Create a scene with one step. Set your channels to where you want to have them. Now save and add this scene to your live screen. And now
right-click and select "Fade in" and/or "Fade out".
Done
maybe hard to understand but easy to do if you know how
Lighter007