For installation of CopyMask2Layer perform the following steps

(1) copy the file CopyMask2Layer.jsxbin into the folder
"Support Files/Scripts/Script UI Panels" (on Windows) or
"Scripts/Script UI Panels" (on Mac) of your After Effects
installation. 

(2) Start After Effects and make sure that in the preferences 
    (tab "general") the option "Allow Scripts to write Files 
    and Access Network" is enabled.


(3) Start CopyMask2Layer (via the menu "window" in After Effects)

