Currently, not a clue. I don't think anyone knew.
Red Dwarf has, presumably, been travelling in a straight line for three million years when Lister awakes from stasis, presumably to stay out of the space lanes to stop radiation contamination. Then, of course, it hit light speed and Holly tried to turn around. I don't think he managed it (Lister did say it would take two weeks to turn, but he may have been exaggerating).
After that, we know that they found remnants from Earth - simulants, gelfs, derelicts etc, and of course the Nova 5 and Kryten. In "Infinity Welcomes Careful Drivers" it alludes to how far the Nova 5 came out from Earth in order to ignite stars for the Cola company, but I forget how far that was (and it's a different continuation).
After that, of course, Red Dwarf is stolen by the nanites so the crew move to Starbug and enter stasis for 200 years, after which they turn around and enter stasis for presumably another 200 years. We also have the period where the crew go into stasis so they can get to the Nova 6.
Put bluntly, I don't think anybody has a clue, but right now (as of The Promised Land) they're probably roughly back where the Nova 5 was, assuming the Nova 6's mission and area it was in was similar.