Instructions
Compete in as many duels as you can. Every time you duel, you have a chance of winning a new card or booster pack. These booster packs sometimes contain Synchro Monsters and the special Tuner cards that you need to summon them. Apart from the duels that move the plot forward, there are countless optional duels you can do with the people you meet throughout the game.
Add multiple Tuner cards and other non-Tuner monster cards to your deck when you equip your Synchro Monster. When summoning a Synchro Monster, you need to look at its total level to determine what cards you will tribute to summon it. If the Synchro Monster is level 25, the total of the levels of the tribute cards must be 25. For example, if your Tuner card is level 15, you need to tribute a non-Tuner monster card that is level 10 before you can summon the Synchro Monster.
Join any duel as you normally would. Play through the duel until you draw the Synchro Monster, a Tuner card and enough non-Tuner monsters to summon it. Play the Tuner card and the monster cards -- as long as those cards survive, you will be able to summon your Synchro Monster on your next turn.