In addition to placing the health bar, to get some experience using text, let's use that as well:
With the Canvas object selected, create a text object by navigating to GameObject | UI | Text.
Now, it may be hard to see it being added at first, so let's first change the color of the text. Select the Text object, and go to its Text component. Once there, change the Color property to white:
At this point, you'll notice that the text is actually backwards. Fixing this is very simple; just change the Rect Transform module on it to have a Y Rotation value of
180
.For our purposes, we will have this be displayed in the center of our object. To do this, we can just...