There are primarily three stages of hopping boiling, flavor and finishing. You will add these different hop ingredients to the wort during different times of the boil.
Hops come in several different forms but are essentially the same.
Hop plugs and pellets are more compact than whole hop flowers and also preserve flavor longer. Most beer kits will have been already hopped for you. These pre-hopped extracts will have a bittering hop already added, but do not contain a flavor and finishing hop. If you desire added bouquet these hops must be added later in the boil. Add boiling hops and boil for 30 more minutes.