Manually edit .project and under <natures> add this:
Code:
<nature>edu.wpi.first.wpilib.plugins.core.nature.FRCProjectNature</nature>
That lets the WPILib plugin know your project is a robot project so it can add the menu items.
Example
Edit: I realized that I assumed you have the WPILib Eclipse plugin installed. If not, go install the plugin