first give the dashed stroke circle path a 20% transparency
Draw another rectangle the size of your document, to help visualize what you are doing give it no fill and nostroke
place it above the circle and the gradient fill rectangle but under the text art.
select the new rectangle and the circle and the gradient filled rectangle and make a clipping path Command 7 (Mac) or Conrol 7 (PC)
yes you are correct it is not in the tutorial?
I believe the instructions should have told you to place the ellipse in front of the radial gradient and behind the letters, and then reduce its opacity.
With that interpretation there will be rays outside the rectangle, visible on a coloured background.
In order to get rid of them, additional steps are needed, such as a Clipping Mask on top, with the size and position of the rectangle.
I am going to give you another waay of doing this so that it looks like and acts like the tutorial.
after you draw the rectangle and fill it with a gradient go to the toolbar or tool panel
with the rectangle selected near the bottom of the Toolbar is the drawing modes icons select Draw Inside
Now you can make your circle (no need to restack it behind the text art it will be inside the rectangle which is behind the text art already.
then apply the stroke and give it the transparency settings. Notice the dashed corner marks around the rectangle in the screen shot that that indicates the rectangle is set to either draw Inside or draw behind.