You have downloaded an RBZ file - a type of ZIP file - containing the files and folders needed by the plugin [aka an 'extension']. It needs to be 'installed'. SketchUp menu: Window > Extension Manager > Install Extension... [red button] Find the RBZ and install it. Most installed extensions are then immediately available in their [sub]menu items or toolbars - read the usage details for each one. BUT, in the case of most of Fredo's tools [and many of thomthom's and a few other authors] you must also install a set of helper files - in this case: https://sketchucation.com/pluginstore?pln=LibFredo6 After installing the Lib, you are probably best advised to restart SketchUp to ensure everything is synced. You only need to install the Lib once. Unless of course a new version is available, and a particular extensions says it's installation is necessary.