If you are using a fresh install or a new vgclient.ini file, then the UI section won't be filled out at first. It populates it later. You can, however, manually enter the information.
Replace relevant information (mainly what UI you want to use)
Code:
[UI]
ShellName=CoreUI3
ValidateXML=False
ChatAutojoin=
LoadGameplayWindowsAtStartup=False
PresentLogin=True
GuildNotifyOnline=False
LootFollowsMouse=True
FilterProfanity=False
ShowChatBubbles=True
UseScrollingCombatText=False
UseMultipleLayers=False
iMaxTextColumns=1
ScrollingCombatTextScale=50.000000
MaximuCombatTextDelay=1.000000
CombatTextAlpha=1.000000
ScrollRateBeforeBranching=1.000000
DrawTargtingBillboards=True
DrawTargetingBillboards=True