First you will need the Voyager models from this pak (Thanks to Doctor of Space).
Download it and put it in the SpaceEngine\addons folder.
2nd put the VoyagerProbesPositions.pak in the SpaceEngine\addons folder.
Start SE and choose Voyager01 or Voyager02 from the Ctrl+F3 Spacecrafts\Other Menu. Press G to go to it and then press Ctrl+ \ to reset to current time. Enjoy the view:
Trajectory data were obtained from Nasa's Jet Propulsion Laboratory Hyperbolic Orbital Elements page. They are rather old but if anyone can find a more recent set, please be my guest and I'll be more than happy to update them .