I found the quickest way to win the 5 matches against the AI was to have the score limit set to one round. To do this from the menu, you need to:
-'Play Uno' from the Main Menu
- Select your deck (I just used the regular set)
-Then at the bottom where it says 'Score Limit', set to 'One Round' and then start game.
I did find this taken a little while as the AI seemed quite good but too get the five wins this certainly seemed the quickest.