The Pop-up menu style button is for sub-menu items.
Click on the Help button in the same dialog window.
Then Search for "navigation" and open Navigation Bars.
Read that.
Finally, on that page is a link to "Creating your own MouseOver Buttons".
This is the part you need to understand the most.
In a nutshell:
Fish shape and text grouped on MouseOff layer.
Clone and move to MouseOver layer.
Change colour of fish.
Soft-group items on both layers.
Right-click Create Navigation Bar.
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