Add powdered sugar (do not use generic brands, they will clump..I like Dominos) about 1/4 cup at a time. Mix with greased spoon at first, then use greased hands to knead fondant like bread. Once it has the consistancy of play-dough it's ready to roll out. You can leave it white or add your colors at this point.
Grease rolling pin and space that you will be rolling your fondant on. If fondant is too sticky add powdered sugar, if its too dry add a couple drops of water..if it's too hard microwave for 10 seconds.
After it's rolled out to about 1/4 in thick you can gently place it on top of your cake. Careful not to tear the fondant, I usually lay half on my arm and slowly spread it over the cake. Smooth fondant, starting at the top and move carefully down the sides. You can use a smoothing tool or your hands. I like using my hands and then using a small rolling pin to smooth it.
Cut off remaining edges off the bottom..I like using a pizza cutter :) Save extras for decorations!