If you're new to using modern sonic, if you're on mobile and is on a level, press menu, if your on the start screen, eh i mean if you just launched the game, press on the options button, press it until the yellow thing is on the options text, press the corner button, and now press the corner in the touch screen options, and press corner on the touch controls, and press on the use preset and tap the corner, and press until you see the none text, and now you press on the customize text, and now press the corner, and press the plus button that is green, and now use the scroll thing to scroll down, and when you see custom action 1, thats what you want, now press on it and press add, and now you can move it to everything you want to!