Install:

Copy the .dlt file that correspond to your version of 3ds Max to the
/plugins/ folder located in the root folder of your 3ds Max install.

In the newer versions of 3ds Max, the default plugins folder can be 
modified. If your plugin isn't loading, it might be because this folder 
has been changed. To find the correct folder, navigate to: 
"Customize -> Configure User and System Paths -> 3rd Party Plug-Ins".