Can someone tell me how to soften icing?

I made a lot of cakes for Xmas and have plenty of unused icing (I've added a colour to it). When I noticed that I'm not going to use it at the time, I've stored it in the freezer for a month. Then I took it out and was going to bake a cake using it (it was perfect defrosted), but something came up and I didn't. I left it outside and forgot. It was wrapped in cling film in the freezer and out. It stayed in the room temperature till today and got very hard. I have 2 pieces of about 1kg each to refresh and use, as I have to bake a cake. The icing has been bought ready made from the store. Can someone tell me how to make it soft? I am not going to use it to cover the cake - just to mold it into flower shapes, so it doesn't have to look nice.