I'm feeling somewhat THICK because I cannot find out what button to press to change screens whilst riding. I'm inundated with information on setting up or configuring screens but so far failed to find out how to change the screen forward and back. I've configured my 1st screen and added a 2nd screen - so what now? I press the lower right button when I start my ride and on the 530 is my 1st screen. Now, whilst riding, I want to switch to my second screen, and probably back to my first screen. How is this done?