How do I make the usual options buttons?

Does anyone here have a GUI script that could … for example …turn up the volume of my game permanently, until the slider goes down again?
This is just an example so I can make some buttons and such for an options menu.

Sorry for the amateur question, I hope someone can help!

The idea would be to have a class with all game info as static so that they are accessible anywhere and last all the game like volume or other settings.

Then use a slider, your value altered in one scene will propagate to the next.