Firstly, if you log-in between now and 13th March 2017 at 6:59 AM (UTC), you will receive 10 Dueling Crests, which restore 3 Dueling Swords each. These can be claimed from the Present List.
Secondly, to encourage you to use your Dueling Crests, there will be special Arena Quests that last until the end of this month. The great thing about these quests is that they grant more Hero Feathers (1000 from the initial quests) and Dueling Crests.
Given that the Arena is the best place to earn feathers (which are used to increase a Hero’s rarity), now’s a great chance to get accustomed to the system and increase your Arena Tier while you’re there!