First you need to add the Yamaha to the devices. Next, assuming the 890 is similar to the 880, you can use the Yamaha volume for everything. When you setup an activity manually, you get a choice like:
"To Play CD, which device do you use to control the volume?"
At this point, you just choose the Yamaha from the menu.
Also, on the home page after you sign in, there is a "Support Center" link on the top of the page. If you click it, in the reference section, you can download the manual.
As a side note, this is one of the most important features of any universal and the Harmonys have a way to do it.