Salutations.
If you're playing the official Brawl Minus 3.5, and you haven't been on Nintendo's Wifi with your current Brawl save data, then all you have to do is load up Brawl Minus and click connect to wifi. If you have connected to Nintendo's Wifi in the past, I still recommend to do the above suggestion. If it doesn't work, then you'll need to create another Brawl save data and repeat.