Um, are you perchance responding in the wrong topic? This sounds like discussion of your difficulties uploading a model for us to examine in Wire framework persisting after solid shape deleted or hidden - #9 by spogadog. Regarding that, you want to click this icon at the top of the message edit window
That will open a dialog asking you to select the file. In some cases you can drag and drop a file onto the message edit window here on the forum and that will upload it automatically without opening the dialog, but the dialog will always work.
Regarding installing plugins, please read what Geo posted. If the plugin file is a .rb file, you need to place it into the appropriate folder, but that isn’t accomplished by dragging it onto the SketchUp icon! If the plugin is a .rbz file, you install it using the Preferences->Extensions menu in SketchUp, which again isn’t drag-n-drop.