Ragnarok Mobile Mission Board Quests are unlocked at base level 15, just speak to the NPC next to the mission board.
Unlock the Mission Board Quests at Level 15
You can find the mission board in the center of Prontera. Once you are LvL 15 speak to the girl next to her and she will unlock the mission board quests for you.
Board Quest Rewards
Complete 10 of these quests per day for bonus base and job exp and consumables including that shiny lightning chain that doubles exp and loot during battle! (Note: it also consumes stamina at double the rate.)
Feeling lazy? Once you have meatballs you can use them to instantly complete these quests.