To increase your VIP level, you need to accumulate and use VIP points. Please note that the maximum VIP level is 25. 

-Click on the VIP button under the Commander's avatar, and you will see your current VIP level along with the number of points required to advance to the next level.
-Click on "Acquire Points" from the VIP screen, where you can see and use the VIP points items in your backpack. You can also purchase and use VIP points items directly with gold immediately. 
-Using VIP point items directly from your backpack, which can be obtained through events, tasks, and other means.
-Daily login gives you VIP points; increasing the consecutive days of logging in will earn you more VIP points.