Download the Poliigon Material Converter for 3DS Max.

To install the material converter, open the zip folder and drag in the installation file into the viewport in Max.

Add the Poliigon toolbar button by going to the customize menu, then select customize user interface. From there, select the toolbars tab, find Poliigon in the catagory drop down and then finally, drag the Material Converter button to somewhere on your toolbar.

Click on the new Material Converter button, select the location of your textures then check that the correct renderer is assigned, and finally click on 'Convert!'

Open the material editor, under the new 'Temporary Library' you will see your imported materials, drag the desired material into the slate editor then, with the target object selected, right mouse button on the material and assign it to the selection