Using your stick over to one side, lift the track off of the ground.
With prybar or crowbar get the track engaged onto the sprocket
Gently using a prybar add pressure and lever or guide the track back onto the idler while a helper engages traction to that track.
Generally the track will pop back onto the idler wheel.
Easier if you can release the pressure on the tensioner.
In future when turning use your stick to lift the inner track off of the ground all while driving the outer and gently turning with the stick.
Sharp aggressive turns with right track in reverse and left in fwd will detrack just about any tracked machine if everything is not 'just perfect'. Also those side loads are hard on the whole undercarriage components.
I have watched a good operator turn an old worn machine 90 degrees when the tracks were so loose and worn that the track chains sagged almost 6-8" (rubbed on the tensioners) with the above technique.
Good luck!