Change Size of Game Screens
Utage’s default screen size is 800 x 600. In general, the screen size is configured when the Utage project is created; however, it can also be changed afterward.
Screen sizes can be configured from each camera. Select the SpriteCamera and UICamera and configure the GameScreen Width and Height.
Configure Range for Click Detection
You also need to adjust the size of collisions for detecting screen clicks.
Adjust UI Size
To adjust the size of message windows, etc. please change the size of each sprite within the scenes and prefabs.Reference