Can I suggest that first you ensure that you have the latest version of SketchUp 8 - Before v8M2 automatic installation was not an option... Now get Thomthom's 'Simple Plugins Installer' liked off the Ruby Index [see menu above]. Download that tool's RBZ archive to your PC. As explained in its download page instructions, use Preferences > Extensions > Install... button and find the file + OK. It automatically installs the file for you. [If you have insufficient 'security permissions' to write to your PLugins folder you will be told - to fix that issue highlight the ../SketchUp../Plugins folder icon and right-click context-menu to Properties > Security > Edit ans set permissions to FULL for everyone including yourself, you might need to have Admin privileges to do this change.] Assuming you have now got 'Simple Plugins Installer' installed then there'll be a new Plugins menu submenu, that has tools which will auto-install any of the four common toolset formats - single file RB/RBS and archives RBZ/ZIP. So now once you have downloaded a toolset you can install it 'stress-free'... However, please read each tool [or support library] download page carefully, and ensure you have any additional supporting files/libs downloaded and installed too... Then all you have to do is read [and understand] the new tool's usage notes so you know which menus/context-menus/toolbars items appear in, how the tool is actually used etc etc...