I KNOW someone can post a tutorial, but I can try to tell you.
Punch two small holes in the card. from the front put one end of the ribbon in each hole.
Cross them in the back
Pull them up from the back in the opposite holes
Smooth the back out as much as you can *it's crossed so it won't smooth all the way flat, just make it neat*
Then trim ends to your liking.
Hope this helps.
Like I said, someone will come along with photos and maybe even a video.