There are 3 basic steps to installation.
The path after unzipping will look something like:
"C:\Program Files\Adobe\Adobe After Effects CC\Support Files\Plug-ins\clintons3d"
The folder contains aex files for CS3 to CS7(CC) all named "colladaImportExport.aex_CSX", where X is the version of After Effects.
A generic 64 bit version is included now (Aug 2015), "colladaImportExport.aex_64bit". It is designed to work with CS5 and up including future versions of CC.
To access security - right click the folder and choose properties then the security tab. Generally, the "Users" group or your user name can be altered to give read and write access to the folder. Use the edit button to set permissions. If there is no Users group you can add your login name with the add button.
The plugin uses scripts to read and write temporary files. The Allow
Scripts to Write must be checked when running AE.
Edit - Preferences - General