This will be a GUI Frame that will act as the background for our eventual health bar. When you resize this, you'll want to make sure you keep the X and Y offset's to 0.
Your first instinct may be to grab the white blocks around your new frame to resize it, but this does not resize your frame properly! All it does is change the "offset" property. (Later, in our code, we'll be changing the "size" property, so let's stay consistent.)
Keep the "offset" at 0, and use the "size" property instead.
Go into the properties window of your frame, and scroll down until you see the "Size" property. Open this up, and then open up the "X" and "Y" properties.
Now, find the "scale" property. The scale is actually really huge by default, so in the example, we've used X: 0.15 and Y: 0.025. Of course, you can use whatever values you like.
Use your mouse to click and drag the Container anywhere on the screen. Most games have health bars in the corners, or at the top or bottom edges of the screen.