When you click on the link, you will be presented with an option to make a copy of that file. You need to do that before you can create your graphics.
The image can be edited by an individual, or by a group. It can be projected for the purpose of class discussion. You can Select All (in the Edit menu) or just select some part, and Copy to Google Slides or Google Docs.
Instead of dragging the blocks from the "box" they're in, I suggest you select the block you need (single click), duplicate it, and drag the copy to where you want it. (Duplicate is an option in the Edit menu.) This way you won't accidentally delete the only instance of that block in your drawing. You can duplicate blocks as many times as you want.
In the 2D images, if you need to rotate the block, select it (single click), grab the handle that sticks out of it, and turn. Or, to be sure you turn exactly 90°, you can select the block, and use the Arrange... menu to choose Rotate... 90° clockwise or counterclockwise.
In the 3D images, do not rotate blocks. Instead, select the version of the block with the orientation you need. In your image, if a block is hidden behind another block when it should not be, you can use the Arrange... menu to choose Order...Bring to Front.