Tip 11-13. The Graphing Calculator et al. - in trying to describe in great detail how to perform the function - skips over one important detail.

Step three reads, "Click Add, and navigate to Applications -> Calculator -> Contents -> Resources in the dialog box that opens."

It's worth noting that this Add button is the one in the Plug-ins section of the Get info window. There's also one in the Languages tab and if, like me, you tend to keep all the sections but General closed, the Plug-ins Add button doesn't jump out at you.

(For that matter, as soon as I saw the path, I assumed we were showing package contents and then scanned back to see this business with the "Add" button and felt completely lost.)