Quick note to make sure we are on same page: "Scenes" are various on/off stages of the effects on a single preset. Changing scenes can turn on/off multiple effects (think: pedals) with a single button press. I don't know your experience or expertise, forgive me if this is "dumbed down." This is a BASIC tutorial - the FX8 can do a LOT.
Quick tutorial, using the FX8-Edit app:
1. start with a blank preset
2. to the right of the picture of the FX8 unit, there are 8 spots where you can drop effects. Immediately above are 6 screen tabs marked "Effects", "Config", "Footswitches", "Gate/Out", "Controllers", and "Looper." Make sure you are in the "Effects" tab - it lights up in yellow. Right click the mouse and drop an effect in each of the effects spots below those tabs. They will all be lit up in color. Your actual FX8 unit will still look blank.
3. Click on the "Config" tab and decide the balance of pre/post effects. Pre is like plugging into the front of your amp, post is like plugging into the effects loop. Sometimes makes a huge difference. "Series" essentially means daisy-chained, plugging one effect into the next; parallel is running them at the same time, but not "into" each other.
4. Click on the "Footswitches" tab. Right click on each of the spots and assign the effects you loaded into the appropriate spot. NOW you will see them appear on the screen of your actual FX8 unit.
5. Hit the "Save" button on the app.
6. Set "Scene Select" to 1. Just as an example, turn OFF all effects you loaded, except for one. Turn them on and off by clicking on the effect and pushing the space bar on your keyboard. Hit "Save."
7. Now go to Scene 2. All of the effects probably lit up in color again, meaning they are all on. This time, turn two or three effects off and hit "Save" again.
That's enough for you to get the idea. Press Scene 1 and the only effect that is on is the one you did in step 6. Press Scene 2 and you'll see the effects change again to match what you set-up in step 7. Press Scene 3 and they'll all light up.
The X/Y sliders give you the option to set the knobs differently on each effect, giving you two different settings on the same effect. When you set up your scenes, in addition to turning effects off and on, you can choose the X or Y version for each.
Again, this was a BASIC effects/scene set-up. You can go really crazy with the FX8.
With regards to the rolling through presets, the F1, F2 and F3 footswitches on the FX8 unit can be assigned a couple of different ways to perform different functions. Check out Chapter5 (page 21) in the FX8 owner's manual to configure it how you like.
I hope this helped! Welcome to the Fractal Forum!