Playback levels for each track are set with their respective track faders so just turn those down as required.
The R/L meter bars on the far right of the screen reflect what the monitor system is 'seeing', which by default is the stereo bus. The signal level from the stereo bus is controlled by the individual track faders and the stereo fader.
If you're worried about the meters flashing red, this is normal for an imported track which is just touching the max 0dB level. It should not normally be a problem.
If you're finding the track signal is overloading the track EQ and causing distortion, use the digital trim level in the mixer screen.
If you really want to reduce the recorded level, you can do what FP suggested, or bounce the imported track to another track with the bounce source fader(s) or Bounce Master level (shown in the bounce screen via F4) set as required.
The block diagram helps to visualise the different possibilities.