Skelion is a plugin of SketchUp. It means you need SketchUp running on your computer
to install it. Follow the normal procces to install plugins on Sketchup (Watch manual or SketchUp online help).
Sketchup Make or Pro 2017 and later Internet Explorer 11 in Windows OS
(Reload the page if link doesn't work. Use "save link as" to save as .rbz and avoid automatic unzipping.)
By purchasing a Skelion license, you will automatically receive a Skelion Pro & Support Package for a year. To keep benefiting of it you can annually renew the package.