Profile ID is an identifier used to locate a player's game account. It is a 6-letter combination (ABCDEF) unique to each player, and it can not be changed.
You can find your Profile ID in a couple of places:
1. In the bottom-right corner of your loading screen.
2. In your Profile
Click on the icon of your warlord in the upper-left corner of the main screen, and you will find your ID in the Profile window.