Go to Single player, and pick a "player vs CPU" game. Press
at the character selection screen to change the difficulty to beginner. Pick Sabrewulf as your character and anyone as the enemy. Defeat the enemy.
Just button mash through the match and you should win.
is especially hard for the AI to counter, although it does little damage. If that's too much trouble, you could also go to multiplayer, choose local play and use a second controller to give yourself a win.