I use a set of HTML help files which I downloaded from the web some time back. I have uploaded it to the forum before but here it is again. All of the core commands are covered and examples provided.
I would recommend you make a shortcut to:
yourpathTcl HTML HelpTclCmdcontents.htm
I put my shortcut on the status bar at the bottom of my Windows screen. That way help is always available without having to close other Windows to get to it.
ZIP file of HTML doc should you wish to install locally.