MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
Depending on what version of SketchUp you have, there are different ways to do it. If you download the most recent version, there is an "extension warehouse" under your "window" option. Go there, and in the search box, type in STL and you should get a SketchUp team extension that you can download for free that will import/export STLs.