You need to prepare the save data of this game beforehand, and it will not work with the DLC data alone.
When you load the save data, the DLC data will be loaded together with it.
The elements included in the DLC are as follows.
Unlock the hidden "Stranger" aircraft.
2P invincibility mode (2Ps will become invincible if you hold down Start and press A when selecting their aircraft)
Unlock all score attack stages (by default, you can only select stage 4, but with the DLC, you can unlock stages 5 through 7)
Cumulative score display will be turned on (cumulative score will be displayed in the score ranking).
As for the Stranger, it is the same plane that is unlocked when you clear the game with one credit.