In general these medications are applied by gently spreading the cream onto the skin. Some need massaging into the skin, others do not. Try to always apply these forms of medication to a dry skin.
What if my cat keeps licking them?
If your cat tends to lick the area of application there are several things you can try. Firstly, apply the cream just before giving the cat its food or just before taking him for a walk. This way, he will have something else on its mind then licking the cream off! Secondly, you can try fitting an Elizabethan/buster collar to your cat to prevent the cat reaching the treated area of skin. Not all cats will be happy wearing these collars, but most accept it quite quickly. Thirdly, you can cover the skin with a bandage or boot if it is a foot. This is not always failsafe and it is not easy to apply a bandage without making it too tight or too loose. If the affected area of skin is on the body of the cat you may try putting an old T-shirt on your cat. Finally, in some cases the only solution is to muzzle the cat while the cream takes effect.