I did Carrie's delicious fondant and everything was good but it became hard.Yeap, too much sugar, but I added crisco and still is too stiff. Should I add glicerin? If so how do I incorporate it, should I knead it? Carrie's recipe does not have glicerin, I'm afraid that adding too much crisco will make the fondant tasting horrible.
I don't know what Carrie's fondant is made of but with my marshmallow fondant adding glucose helps soften it. I regularly model things with fondant and keep several large ziploc bags full of balls of colored fondant. Over time these balls get crumbly. I just put shortening on my hands and then knead in glucose a little at a time until it is soft and pliable again. I have also done this with large batches of fondant that did not get used shortly after being made and it worked perfectly. HTH
One thing that helps with marshmallow fondant and that might help with your recipe is to microwave it for a few seconds at a time until it's a little more pliable.