Quit After Effects if it is running. Unpack the archive you've downloaded from and move the file "Limber.jsxbin" to your “ScriptUI Panels” folder, which is located here:

Windows: Program Files\Adobe\Adobe After Effects <version>\Support Files\Scripts

Mac OS: Applications/Adobe After Effects <version>/Scripts

If the ScriptUI Panels folder does not exist, create a folder and name it “ScriptUI Panels”

Go to the General tab of After Effects’ Preferences pane and make sure that ‘Allow Scripts to access the network’ is checked on.

Once installation is finished, run the script in After Effects by clicking Window > Limber