Once you have located the image file and clicked ok, you still need to do two more things in order to see it in the plane object in the viewport. First, click on the ‘assign material to selection’ button (1: circled red) then click the ‘Show map in viewport’ button (2: circled red). It is also a good idea to change the width and height of the plane object to correspond with the image file. In this case it is 1536x1536 pixels.

So that’s our first blueprint set up in max. We don’t want to touch this anymore, so let’s lock it. Right click the plane object and choose ‘Object Properties’. Check the ‘Freeze’ button. This stops the object from being selected. Unfortunately, it also turns the object completely grey, which isn’t too helpful. To remedy this, uncheck the ‘show frozen in grey’ button. Problem solved.