Source
Now that you have downloaded one of the UI mods, what are you suppose to do? Well here is a nice list that Drox posted up for us all. They are fairly simple. However if you have any questions, feel free to let us know. Someone around is sure to be able to answer your questions.
1.Unzip the file using your favorite zip/rar program.
2.Copy the folder included in the zip to your c:\Program Files\Sony\Vanguard\VGUIAssets\Shells folder.
3.Open the c:\Program Files\Sony\Vanguard\bin\vgclient.ini file in a text editor (notepad is fine).
4.In the [UI] section change the shellname to "ShellName=ModFolderName" where ModFolderName is the name of the folder that was in the zip file.
Inside your vgclient file, you will find [General] section, below this fairly large span of text you will find [UI]. Some times, I have found, that after a new patch or full file scan, there is nothing below the [UI]. So here is what it aught to show. You can copy and paist this below the correct section and replace UIName with what ever UI you wish to use.
[UI]
ShellName=UIName
ValidateXML=False
ChatAutojoin=regionsay,auction
LoadGameplayWindowsAtStartup=False
PresentLogin=True
Some things to remember however:
Make sure that you have not accidently doubled the UI folder.
Make sure you modify the ini folder correctly. If there are caps in the name of the mod, you have to include those.