Commodore OS is a pretty good linux to learn common desktop paradigms.
You probably know some of this so forgive me if I get a little too basic.
You can drag windows around by holding the left mouse button down on the title of a window and moving your mouse.
Double clicking on a window title can maximise the window on the screen or restores a window to its previous size.
There are maximise and minimise buttons on the far right of the title bar.
Minimising an app window will hide the app, and it will be represented in the dock with the icon for that app (faded to differentiate it from an actual app launcher). Clicking on that app icon in the dock will restore it.
Just as in MS Windows
ALT + TAB changes application windows to the previous one used.
If you hold ALT every time you hit tab it will cycle through all windows.
The following does something similar to ALT+TAB, but sometimes results in a different ending window layout. I'm not really sure what rule its following.
Super key + TAB
(The Super Key is the branded symbol key close to your space bar. On the C64x it is a C= on most keyboards it is the Windows symbmol)
Control + TAB displays all open windows for the current workspace in COS3 on screen at once that can be selected with your mouse. This is my favourite feature.
There are 4 workspaces, which are like duplicate desktop screens arranged horizontally, that can be accessed from the four squares in the upper left of the top menu panel.
Control + Alt + left/right arrow key also allows you to switch between them. (There are other ways too)
You can drag windows to new workspaces by dragging them off-screen to the next workspace.
You might want to have a look at the cool stuff under "Display Keyboard Shortcuts" accessible in the "Commodore OS" menu available from "System" in the top menu panel.