Cut a length of ribbon, then pull a back-and-forth thread from the ribbon to unravel the end, which will reveal the lengthwise threads:
Cut off the thread that did the unraveling. Now find the approximate middle of the ribbon and begin pulling one (or two) of the lengthwise threads. I find a pair of conventional tweezers helps this part. Pull the thread with one hand and move the gathers down to the middle of the ribbon with the other.
When you’ve ruffled about half of the length of ribbon, repeat from the other end.
Put down a piece of Sticky Strip across the card front or panel. If I want frayed ribbon ends, the Sticky Strip won’t go quite all the way across.
Press the ribbon into the Sticky Strip, carefully placing the ruffles just so or allowing them to fall naturally. (Personally, I don’t fuss too much about this!)