If you didn't check the box during setup, open the CODEX folder on the virtual disc, copy all files inside, and paste them into the folder where the game was installed, overwriting the existing files.
The file name Cobra.Kai.The.Karate.Kid.Saga.Continues-CODEX.rar follows standard scene conventions: Cobra.Kai.The.Karate.Kid.Saga.Continues-CODEX.rar
Right-click the .rar file and select "Extract here." This will usually result in an .iso file (a virtual disc image). If you didn't check the box during setup,