The details of Arena can be viewed from the Get Gold tab under Activity Overview. To enter the Arena, you need to find Mack in the Salvation Town and enter from there.
You can earn Arena Points, Crystals, Island Coins, Gears, and Upgrade Materials in the Arena.

Arena Details:
1. Requirement: After your character reaches Lv.16, you can talk to Mack in Salvation Town to enter the Arena.
2. Battle Rules: in the Arena, you can battle with other survivors, and earn Victory Points for each victory.
3. Settlement Reward: The Settlement Reward will be given out after each season based on the number of Victory Points earned.
4. Point Reward: if you have 0 to 350 Victory Points, then you can pick up the reward once. If you earned more than 350 Victory Points, then the reward will reset each season.
5. Point Reset: At the end of the season, if you have less or equal to 350 Victory Points, then your points will remain the same, but if you have more than 350 Victory Points, then your Victory Points will reset based on the reset rules.
6. Gear Durability: the Gear and Weapon Durability Cost in the Arena is decreased by 90%.
7. Settling Period: the settling starts 5 minutes before a season ends. You will not be able to match other survivors during this period.

You also get daily Victory Chest Reward, which can be claimed after achieving 3 victories in a day, in addition to points rewards. The chest will be send to your mailbox after being claimed.