Material Editor > Get Material or Type button > Material/Map Browser > Browse From group > Select Mtl Library. > File group > Open material library. > File group > Merge
The Merge Material Library dialog lets you merge materials in the open material library with materials in another material library or another Autodesk VIZ or VIZ Render (DRF) scene.
This is a standard Windows file dialog. It lets you select either material library (.mat) files, Autodesk VIZ (.max),
When you click OK, a further Merge dialog is displayed. This lets you select by name the materials you want to merge with the open library.