Very easy if you have followed the below settings. Simply beat the game. You can continue, so don't sweat it if it's your first time playing. Just keep trying until you beat the game. If you're having an issue, practice with one character until you have their moves down.
Note: To make these easier, make sure that you do the following in the Options menu:
Set the difficulty to 1 (Easiest)
Set your players power gauge to MAX
Set your defence to level 8
Set CPU's defence to level 1