This guide explains how you can change in-game resolution.
Guide to Change Resolution
Unfortunally 480p are native graphics, there are no resolution options.
So you can’t change it in the Arena of Kings game.
But you can partially solve the problem.
You can and the resolution is fine, its built for 1920x 1080. Just change your windows settings and play the game.
The game is amazing and has had a much better launch than 99% of games out. Maybe later devs fix it.