In the process Builder, within the step builder Basics tab, you will see a feature called Add Link in iFrame to Step:
You can use this to embed YouTube videos, calendars and much more to the step.
Please note: When you’re embedding a site in an iframe, some sites block embedding some links or URLs by popping the window out automatically or not allowing anything to display. The site may, though, still offer an embed code. Please explore how you can embed a YouTube video, a Google Calendar and other things.
This is what a video looks like in a run, perfect for training processes:
This is what a Google Calendar looks like in a run, perfect for booking appointments:
This is what a website looks like in a run, perfect for filling webforms and reading:
Soon you will be able to put in any standard URL for Vimeo and Youtube, without an embed code.