According to Amazon Canada, you can unlock fighters by simply tapping their amiibo.
"Access a whole new level of fun and smash the competition with this Super Smash Bros amiibo. A former fighter in Andross’ army, Wolf now leads his own mercenary team, and he’s not one you want to cross. Simply tap the amiibo accessory to the NFC touchpoint on your game system to unlock this Space Pirate."
SOURCE
"Access a whole new level of fun and smash the competition with this Super Smash Bros amiibo. A former fighter in Andross’ army, Wolf now leads his own mercenary team, and he’s not one you want to cross. Simply tap the amiibo accessory to the NFC touchpoint on your game system to unlock this Space Pirate."
SOURCE