InfoPath Ribbon Custom Action

I found this article about creating Custom Ribbon Actions for an InfoPath form. What I do not understand is where the Custom Action 'lives'?

<CustomAction Id="Ribbon.InfoPath.Actions.AddCustomButton"
  Location="CommandUI.Ribbon"
  Rights="ManageLists"
  Title="Custom">
  <CommandUIExtension>
    <CommandUIDefinitions>
      <CommandUIDefinition Location="Ribbon.Tabs.InfoPathListDisplayTab.Manage.Controls._children">
        <Button Id="Ribbon.Tabs.InfoPathListDisplayTab.Manage.Custom"
          Sequence="50" Command="CustomButtonCommand"
          Image16by16="/_layouts/images/allcontent16.png"
          Image32by32="/_layouts/images/allcontent32.png"
          LabelText="Custom"
          TemplateAlias="o1"
          ToolTipTitle="Custom" />
      </CommandUIDefinition>
    </CommandUIDefinitions>
    <CommandUIHandlers>
      <CommandUIHandler Command="CustomButtonCommand" CommandAction="" />
    </CommandUIHandlers>
  </CommandUIExtension>
</CustomAction>

Where does this markup live?