Press the TUNER button to activate the built-in tuner.   Play an open string on the guitar, and the tuner will detect and display the note.   The tuner uses a chromatic scale and semi-tones (half-steps) will be preceded by a 'b' on the display.   If the string is slightly out of tune, at least one of the four arrow LEDs at the bottom of the scale will light up.  Two LEDs may light up, indicating that the pitch of the tone is just in between the pitches represented by the two single LEDs.    When the circular tuner LED in the middle lights up, the tone being played is in tune.   Press the TUNER button to exit the tuner.   If the footswitch is connected to the V-AMP, press and hold the DOWN button on the footswitch to turn the tuner on.  Press the DOWN button to turn the tuner off.