These relationships can be one-way (e.g., dropping a package into a mailbox) or two-way (e.g., calling the postal service to see if it was delivered).
Start by creating a box for each concept, each piece of content, and each process. Arrange the boxes based on how they relate to each other. Play. See what reveals itself as you move things around. Try a few different arrangements before you add the arrows.
Keep it simple. The more you add styling and polish, the less you'll feel comfortable changing and collaborating on the diagram.