On the left side of the controller, you’ll see a four-way directional button (known as a D-pad) that lets you maneuver around the screen to select menu items. In the middle, you’ll see a single, lit button with a stylized X on it: This is the Guide button, used to turn the console on and off and to open the Guide or system settings.
On the right side, you’ll see four buttons (A, B, X, and Y) used to take actions on the screen. Typically there will be a guide onscreen for which button to use for a particular action (for example, A to save, B to go back). If you’re in doubt, the A button is usually your first choice to select a menu item that you’ve highlighted on the screen with D-Pad.