So there are actually two separate programs/apps that are being referred to here (maybe technically more, but I'm not entirely familiar with Hololens.)
There's the SketchUp AR premium feature that is built into the free SketchUp Viewer for Android and iPhone. It's pretty cool. It creates an interactive Augmented Reality display of your model, using your phone and camera as a "window" to view your model, "projected" onto a table or some other flat surface. You can walk around the table and whatnot and view your model from different angles. I've heard some reports that the feature is still appearing to be in "beta" mode, which makes it available to everyone. But eventually it will be switched to only being available to Shop, Pro, and Studio subscribers.
The desktop VR SketchUp viewer works with Vive, Rift, WMR, and Hololens. They need to do a better job at linking to the download. It appears on your My account page when you first sign up for the trial. For some reason it's not on the https://www.sketchup.com/download/all page. Here's a link to a direct download for the SketchUp VR viewer https://www.sketchup.com/SketchUpViewerVR-exe (Sorry, I think that's just a Windows link, they don't really link to the program on the website from what I've found. )
I do plan on doing a more in depth tutoiral on the AR/VR features, but you can take a look at my brief overview on the SketchUp 2019 review I wrote up. https://mastersketchup.com/sketchup-2019-subscribe