Honored Contributor
Honored Contributor.vqm is a verilog file. Just add it to the Quartus project just like any other HDL file. (So it's not importing, just adding it as a source file)
Quartus always goes through synthesis first. Since the .vqm is a structural netlist of LUTs and FFs, i.e. it's already been synthesized for the Quartus. All Quartus is doing is reading it in and getting it ready for the fitter, so it should be very fast. Note that you can turn on Assignments -> Settings -> Analysis & Synthesis -> WYSIWYG Resynthesis. That tells Quartus to look at the LUTs/FFs in the .vqm and try to resynthesize them. My experience years ago was that it gave slightly better results than not doing it. The compile time hit isn't bad since it's still just low-level resynthesis. Hope that helps.
