You can use
the instructions here but just don't do the part that deals with incoming calls. And pay attention to the paragraph that begins with "In case you are wondering, yes, it would be possible to tweak this setting to send calls to other places." That will show you how to send the calls to the line port rather than a Google Voice account.
Unfortunately, my writing is more geared toward people who want to know at least a little of the "how and why" behind something, so I don't know if it will be simple enough for you or not.
