open settings:
Click "Calibrate"
Use the VR-Controller and press trigger on two different positions on the ground (as war away from each other as possible). The first click will create a blue dot, the second an orange one - you are finished once you see both spots on the ground with a line between!
You can click again to restart the process
Make sure to mark the real world spots that you used (the position you had your controllers when pressing trigger) and do the same on every PC.
Now Avatar in VR and Person in real world should be at the same position during a collaboration session