There are several ways to finish the edges of satin ribbon so they don't fray. You can go with the heat sealing method that heats the end of the ribbon, using something like a lighter, soldering iron, or an empty hot glue gun. Alternatively, you can go with a binding substance that is painted on. The heat method requires a lot of care and can result in burning of the fabric, but doesn't leave any marks. Often, binding products will leave the fabric darker, so this method requires care and precision.
Trim your ribbon to the desired length and shape. Once you've sealed the edges, you will not be able to change the shape without resealing, and the sealing liquid will not be removable.
Place your scrap paper on a flat surface with the end of the ribbon in the centre. The scrap paper is there to prevent any of the sealing fluid from getting on inappropriate things.
Paint the edge of the ribbon with the fluid from the cut edge to about 1/8-inch inward. You do not want to go inward any further, because it may darken the fabric and create a noticeable line. Take care when applying it to make sure your line is straight and you do not drip any on other parts of the ribbon as it will not be removable.
Leave the ribbon on the paper to dry. Lift the ribbon off the paper every five minutes for the first 15-30 minutes to make sure it doesn't adhere to the paper.
Trim any loose threads off the end of the ribbon, taking care not to clip any of the sealed ribbon off. Your ribbon is now finished and should not fray.
Trim your ribbon so it is to the length you want and the end is the right shape. As with the liquid sealant, you will not be able to change the shape after you have sealed it without cutting the ribbon and resealing it.
Hold your flame or heat source about 1 inch away from the end of the ribbon. Slowly bring it closer to the ribbon until the edge starts to melt, and leave it at that distance while moving the ribbon's edge back and forth to seal across the entire edge.
Keep the ribbon's edge from touching anything until it is completely cool and no longer tacky. If you touch the sealed edge to anything while it is still hot, you will warp the edge of the ribbon.
Try the method you will use on a scrap of ribbon first to make sure it achieves the desired result. The heat method may not work with certain ribbons if they have chemical additives.
When heat sealing, take caution to avoid burning yourself. Keep a fire extinguisher handy when using open flame or other tools that could cause something to ignite.