How do I bring up the "Labels" dialog box for an already saved and opened label document?

For example, I have opened a saved label document displaying only one completed label in the upper left label box. Now, say I wish to duplicate that label to the entire sheet. At this point, how do I bring up the “Labels” dialog box so that I can check the “synchronize contents” box under the options tab in order to perform this? Or is there another way?

I’ve chased goals similar to this in the past, and concluded that you just can’t. Or at least at the times I tried, I failed to find the person who knew how!