Editing STL Files on Sketchup
From Lofaro Lab Wiki
Step 1: Installing SketchUp and SketchUp Plugins
If you haven't install SketchUp by now, click on the following link: \here It will take you to, the download page, choose the SketchUp version that works for your computer and then download it. If you do it accurately, you will see something like
TO install plugins Click on Windows then choose Extension Warehouse, then you can search for the plugin that you want. To import and export STL files we need to install a plugin that converts STL files to Sketchup files. On the Extension warehouse search for "STL import plugin" and then choose SketchUp STL by the sketchup team.