How do I save my model to the library?

You've probably figured this out by now, but for anyone else coming here looking for an answer like I did, here's how:

With your non-dominate hand, have the laser pointer appear by pointing at the model you want to save. 

Then press and hold the trigger on that hand, a radial menu will pop up. 

Save will be one of those options, release the trigger on the highlighted option you want. 

There's also an export option in that menu. The saved model will now be in your library. You can open the model by opening the library, grabbing the sphere with the model you want to load in it, and then throwing it at the ground to crack it open.