If you find yourself using a menu command (eg Word Count) frequently, you can customise your toolbars to include a shortcut button to execute that command.

First, go to Tools/Cusomize and then click on the Commands tab of the dialogue box that pops up.

From the list of Categories, select the one you want, in this case, Tools, and then scroll down the list in the Commands window until you see Word Count. 

Select it.

Once you have selected the command you want, simply drag it to wherever you want it to be on your toolbar... the button will appear like magic!

If you want to modify the way the button looks, keep the Customize window open, and click on it (the button, that is!).  As soon as you do that, the 'Modify' option in the Customize dialogue box will be activated: If you now click on Modify Selection, you'll get a menu that allows you to change the button image, as well as to decide whether you want text on it as well.

If you only want the icon, choose 'Default Style' after choosing your image.

If, after all this, you decide you don't want the button on your toolbar after all,  delete it by holding down ALT and dragging it off!