You can override 4 methods of SKScene to detect user touch
class GameScene: SKScene {
    
    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
    }
    
    override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {
        
    }
    
    override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
        
    }
    
    override func touchesCancelled(touches: Set<UITouch>?, withEvent event: UIEvent?) {
    
    }
}
Please note that each method receives a
touchesparameter which (under particular circumstances) can contain more then one single touch event.