Use Stellarium, not SatTrack.
Start Stellarium.
[F6] Ensure location is correct.
[Ctrl+Z] Ensure Satellite Hints are displayed.
[F2] Open Configuration Window.
Plugins ⇒ Satellites ⇒ configure
Settings tab ⇒ Updates ⇒ Update now
Settings tab ⇒ Orbit line ⇒ turn off
Settings tab ⇒ Realistic mode ⇒ turn on
Iridium flares tab ⇒ Predict Iridium flares
Select whatever one you want to track.