There is some different way to install Plugins (Extension) in Sketchup
install Downloaded (.Rbz Extensions) plugins in sketchup.
►In the menu bar, follow >> Window >> Preferences.
►Click on Preferences now dialog box is displayed.
►Click on Extensions. The Extensions panel is displayed.
►Click on the Install Extension button browse the plugin (.Rbz) and click on open.
►Do you want to install Extension [Yes]
Some time you need to restart sketchup after installation of plugin or sometime need to enable the plugin from here.
Most Popular sketchup website for finding and Downloading Sketchup Plugins
Install Plugin using Sketchup Extensions Warehouse.
►In the menu bar, follow >> Window >> Extension Warehouse. Click on “Extension Warehouse” and sign in with you Google or Tumblr account.
►Find the Extension and click on install
►Restart sketchup and Enjoy!
install (.Rb Extensions) plugins in sketchup.
If you have .rb extension file plugin you can install the plugin by placing the plugin file into right plugin folder. If you have .zip file please extract before placing. & then restart sketchup.
Folder path (windows)
You will have to enable the ‘hidden items’ option before you could go to this location
For sketchup 2016, 2015, 2014
For sketchup 2013
C:\Program Files\Sketchup\Sketchup 2013\Plugins.
For Version 8 & older
C:\Program Files\Google\Google Sketchup # \Plugins.
Folder path (Mac)
Version 2013 and newer;
[User name]/Library/Application Support/Google Sketchup #/Sketchup/plugins