The Action Bar is the bar that runs along the bottom of the interface. It used to be where all of the program's tools were accessed, so it's kind of an archaic term.
Most tools in current versions of the program are accessed now via the Toolbar, which runs along the right side of the interface. Motion Tracking can be found under the Tools button on this Toolbar.
Hi, running into this same issue and am still very unclear where this action bar is. Which "interface" are you talking about steve? Are you able to include a screengrab?
Alternatively if anyone can just say or show with an image where to access Tools > Motion Tracking that would do it.
Import your video clip to the timeline. Select the clip. In the action bar, select Tools > Motion Tracking. Click Select Object. A resizeable frame appears in the monitor. You can resize the frame by dragging on the corner circles.