Puppies are always licking things. That makes it easy to administer liquid medication. They will usually take it right off the spoon. If that doesn't work, hide the medicine in applesauce or some other food. The same goes for pills. Your puppy may not even notice.

Administering medication directly:
However, some puppies are sensitive to tampered food and resist medicine. In these cases, there are more direct ways to administer medications.
For liquids, tip your puppy's head back. Use one hand to lift the upper lip on one side of the mouth while holding the top of the muzzle, while the other hand squeezes the medicine into the pouch formed by the cheek and teeth and steadies the lower part of the muzzle. Once the medicine is in, continue to hold your puppy's head back while stroking his throat to encourage him to swallow.
For pills, wrap one hand over the top of the muzzle while using the other hand, holding the pill between the thumb and forefinger, to gently but firmly pull down on the lower jaw. When your puppy's mouth is open, reach in and place the pill as far back on the tongue as you can. Then hold his mouth shut, tip his head back and stroke his throat to encourage him to swallow.