How do I add an I cord as the top of a bag?

I have been making the booga bag version of bags and have enlarged the pattern for a larger tote type bag etc. A friend has told me that I should add an I cord on the top of the totes to give them a more finished look. She said it can be knitted on. She would show me, but cannot do so for a few days! I really want to finish this thing.

So if you know what I am talking about and can help or give me a link to a place that could I would appreciate it!

I know how to do the I cord with dp needles, but it sounded like this was something I could do before casting off?

This sounds like what you want to do.

Thanks! Now that I know what to call it officially, I did a search and found this!

I had to rt click on the video link and save it to get it to open. But I think I understand it now! Just need to know if I cut off the working yarn that I was using on my circulars and then cast on my dp’s to start the I cord. Or do I leave that working yarn on my circular, and start new on my dp’s for the I cord?

http://www.knittingatknoon.com/atticord.html

It says this in the second paragraph:

Break the yarn, and cast 3 stitches onto a double-point needle.