So glad the CM Organizer is helpful to you!
“Use with” is a way to have one resource start at the same time another comes onto your schedule. So, for example, let’s say you want to start reading the book Pyramid at the same time you start Boy of the Pyramids. You would schedule Pyramid to “Use with” Boy of the Pyramids. When Boy of the Pyramids starts, Pyramid will also start.
“Use with” is especially helpful when you schedule with the “Start after” option. In the above example, let’s say you want Boy of the Pyramids to start after you finish reading Genesis in the Bible, but you’re not sure how long it’s going to take to complete Genesis. So you would schedule Boy of the Pyramids to “Start after” Genesis, and Pyramid to “Use with” Boy of the Pyramids. When you finish Genesis, both Boy of the Pyramids and Pyramid start.