Fusion 360: Introduction to CAD, CAM, and CAE

Unlike any other tool of its kind, Autodesk Fusion 360 connects CAD, CAM, and CAE in a single cloud-based platform that works on both Mac and PC. In this course, you will explore the basics of designing for manufacture, while designing a Formula SAE steering wheel. You'll design, validate through simulation, render, animate, program a CNC machine, and create a detailed drawing--all while learning industry skills that span the entire digital manufacturing process. Learn how Fusion 360 connects the entire product development process by using the first 3D design, manufacturing, and engineering tool of its kind. 

In the video Create a box primitive. why we create a new component?
After uploading the STL file and choosing 3D Print in the File drop down I have encountered this problem: when I clik on the Grip Top and select Preview Mesh, the Number of Triangles remains 0. It's the same when I set Refinement to High, Medium, Low. PPlease, what can I do to fix it? Thank you for your help.
Good course for beginners to see what Fusion 360 can do for you.