Take the length of your spool of ribbon and divide by two. For a 26 yard spool, the measurement is 13 yards. Remove this amount of ribbon from the spool and leave the rest on the spool. You can remove the second piece of ribbon from the spool, but the pieces tend to get tangled as you fold
them. We found that having one piece on the spool allowed us to untangle the ribbons more easily.
You're simply going to fold the two pieces of ribbon together using a technique you probably used in school as a kid. Start by placing one end of piece one on top of one end of piece two, at a 90 degree angle. Secure the ends together with tape.
Fold piece one back over top of piece two.
Now, fold piece two back over top of piece one. Continue in this manner until all the ribbon has been folded. Always fold in the same direction (that is, always towards you or always away from you).
Every tenth fold or so, you'll have to untangle the ribbon - just move the piece that's on the spool.
When you get to the end, secure the ends with tape.