The easiest way to initially learn how to use Hook is probably by using its menu bar icon. To link items together, just drag and drop them onto Hook’s menu bar icon: either in one fell swoop (for mesh linking), or one item followed by one or more items. Works with files, web browser addresses, emails and more. Here’s a screencast demonstrating that.
After hooking things together with the menu bar icon, select one of the items and bring up Hook’s contextual popup window (⌘⇧SPACE) to see what’s hooked (i.e., what you’ve bidirectionally linked).
Even once you’re an expert with Hook, its menu bar icon/window remains a very handy way to link multiple things together.
See what people are saying about this on Hook’s forum.