I agree with Tom's explanation.
The expression "take it up a notch" also means 'to try harder / make more effort / to make something more exciting, intense, or interesting'.
The expression is sometimes written as "Kick it up a notch". It has the same meaning as "take it up a notch".
The sports team was losing the game, so the leader of the team told the other players to "take/kick it up a notch".