I suppose this guide is a PNG file?
Instead of having to find and drag a temple file in your project, you could also create a black clip on top of the Timeline and apply this Filter Set:
608x1080_Template.zip (561 Bytes)
(works on 1920x1080 projects)
It is set to obscure the left and right sides of the screen and leave a 608x1080 bright area in the middle. But you can of course modify these values and save it as a new Filter Set. If you never used the Filter Set feature, you can find instructions on this documentation page.