DISCLAIMER: Official texture template was not released yet so keep in mind that errors may appear if something changes to the external model of the Thunder and textures need to be reworked. Also there may be bugs.
Put the folder in: C:\Users\USERNAME\Saved Games\DCS.openbeta\Liveries\JF-17
If folders Liveries or JF-17 don't exist, create them.
For steam version, the path will be: C:\Users\USERNAME\Saved Games\DCS\Liveries\JF-17