Pre-wash both the curtains and the ribbons, and then do the sewing. They will shrink differently, so if not pre-washed you won't know what you'll get.

Personally, I wouldn't use fabric glue. I find it bulky, messy, and unreliable.

Mary c is right about washing both the fabric and ribbons. And if you sew, you should sew them in. Personally, I think using glue is much messier and harder than sewing. However, how often do you really wash curtains, anyway, so maybe the glue would be fine.

The curtains you linked are cute; I hope you have fun making them and enjoy having them in your home. It's a good idea to embellish store bought.
Sherry

Get some stitch witchery. You place it on your curtain and the ribbon on top and iron. Directions come with it so read and follow directions. It comes in different widths so get one that is the same size or a bit smaller than your ribbon.
I agree with Patty. I would use gros grain ribbon not satin

Thanks for your help! The curtains are washable and I did get grosgrain ribbon.

I know that the curtains won't be washed all that frequently, but because they are white and in a kid's room, I just have to make sure that everything will hold up.

I'll definitely pre-wash everything, just to play it safe.

I'll post a picture as soon as I get this project done. I'm shooting for this weekend, but who knows...

take a look at this site, they offer many beautiful jacquard woven ribbons.

Here is a link that might be useful: ribbon.calhk.com