Unzip it anywhere you prefer, there will be a folder named Release,
and inside it another folder named GpkFiles.
Navigate to and enter the S1UI folder of TERA:
S1Game > CookedPC > Art_Data > Packages > S1UI
C:\Nova_Tera\S1Game\CookedPC\Art_Data\Packages\S1UI
Copy all the files inside the S1UI folder and paste them into the GpkFiles folder.
After copying everything, go back to the Release folder and run the file ActivateGPUS1UI.exe as an administrator.
Wait until the "black" window appears with the message Done!
After the process is complete, close the black window of "ActivateGPUS1UI".
If prompted to replace the files, confirm!