1.Install Corel Painter 2017 (Select I have a serial)
  Use the Keygen to Generate your serial
2.Start Corel Painter and click on Other Activation Options (bottom left)
  Select Contact Corel
3.Copy Your Installation Code into XF keygen and generate your Activation Code
  Copy it back into Corel Activation Window

4.That's it, Enjoy it

NB : if you already instlled as trial :
      you need to click the Turquoise Buy Painter button, then you get 
      the screen with the Enter Serial or Buy.. 
      and from there works the same to activate.
