You'll need:
Pair of jeans
Lace
Scissors
Heat Bond
Iron
Scrap Sheet of Paper

Turn your jeans inside out.
Measure the lace around the bottom of each jean cuff and cut it so it overlaps a bit.

Cut a piece of Heat Bond to fit the length of the lace.

Place a piece of paper on your ironing board, then your lace, then the Heat Bond over the top. The reason why you have paper on the bottom is to ensure the Heat Bond doesn't stick through your lace to the ironing board. Now, use your iron to adhere the Heat Bond to the lace. Repeat for the other cuff.

Now you're ready to iron on the lace to the bottom of the cuff.
Make sure your jeans are inside out.
Remove the paper backing from the Heat Bond.
Place the shiny side down on the jean cuff.
I put mine above the hem.
Lay a piece of paper over the lace so the Heat Bond doesn't stick to your iron.
Use your iron to adhere the lace to your jean cuff. Rotate the cuff around and iron the other side. Make sure you rotate the cuff around the front too so the lace adheres.
You'll want to make sure your lace overlaps at the seam so you don't have a visible edge.
Repeat for the other cuff.

Yer done!

Put on your jeans and roll up your cuffs.

Yer cute!