In the Desktop app, click the 'ACS ChemWorx' menu at the top left of the window, then click "Plugins" and then click "Configure MS Word".
In the pop-up window, click "Configure Plugin". A new window will appear.
Note: On a Mac, the buttons will say "Install for 2008" or "Install for 2011"
If you already have the plugin installed, you will see an Uninstall option. If you do not have the plugin installed, you will see the Install option.