Sorry - do you have homemade buttercream, or homemade royal icing? You should be using buttercream to cover a cake, not royal icing (it will dry rock hard). You should also thin your icing a bit to ice your cake - the recipe usually makes stiff icing. You can use a tablespoon of milk at a time per cup of icing to thin it out. I usually use medium consistency to ice my cake . . . some people use thin, but I've never had good luck with thin consistency. Hope that helps!
i just iced a whole cake with royal icing..a tablespoon of what..?? i'm kinda new to this.. 
..thanks so much for the help.. No problem! You aren't the first person who has mistakenly used Royal Icing to cover a cake. There is a story on the worst cakes posting (i've lost the thread, but if you find it, it is hysterical) where someone tells the story of their first cake they did in royal icing, and how it was so hard you could chip a tooth on it, and her husband was so sweet and said how great it was! Royal icing is primarily used for cookies, or accents on cakes, but not usually as a base for icing cakes because of how hard it dries. Here is a good recipe you can use for Buttercream:
1/2 c. butter
1/2 c. shortening
1 tsp vanilla
3 tbs milk
1 lb powdered sugar (sifted)
Cream butter and shortening. Add vanilla. Slowly add sugar and milk. Good luck!
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