Ok, I figured out how to dial from Outlook...but only from Office365.
There are a couple of ways.
1. Install the PureCloud Desktop application and set it as the Default Program for Tel: and URL dialing (Default programs in the Windows Control Panel). That way, when you click on a contacts phone number in outlook.office365 it will allow you to place the call through PureCloud. That should work from any browser that supports Office365.
2. Chrome only...you can install the PureCloud for Chrome app (https://help.mypurecloud.com/articles/install-purecloud-for-chrome/). When it is running as your Client, you can highlight a phone number in Outlook.Office365, right-click, and choose Make a Call from the context menu. (That works on any web page in Chrome when the PureCloud for Chrome app is running).
I can't find a way to use the desktop version of Outlook for click-to-dial.