In order to access Achievement System, you have to go to the Imperial Capital Randall and locate the Administration Office. Here's a simple guide that will show you on how to access the Achievement System
1. Launch your Brave Frontier app and tap "Imperial Capital Randall".
2. Go to the "Akras Summoner's Hall Administration Office".
3. There are four buttons in Administration Office. To access the Achievement System, tap "Missions".
4. Inside, you can check the Challenges, Records, Trade your items for Merit Points and event exchange your points for special items.
To learn more about the Achievement System, you can visit any of the articles below.