Open Lightroom and in the menu go to Edit->Preferences...
In the "Additional External Editor" section, press the "Choose" button on the right for choosing the application. A new dialog will pop up asking for the location of the program to run.
PortraitPro Studio 17 is usually located at "C:\Program Files\PortraitPro Studio 17\PortraitProStudio.exe".
PortraitPro Studio Trial 17 is usually located at "C:\Program Files\PortraitPro Studio 17 Trial\PortraitProStudioTrial.exe".
PortraitPro Studio Max 17 is usually located at "C:\Program Files\PortraitPro Studio Max 17\PortraitProStudioMax.exe"
To see an example screenshot with the correct file selected click the image here
Try pasting in these paths if you are not sure. Then press "Choose" to dismiss the dialog.
For the "File Format" please select TIFF. The other settings can be chosen as you wish (for example: "Color Space": sRGB, "Bit Depth":8 bits/component, "Resolution":240, "Compression": LZW ).
Press the "OK" button to dismiss the Preferences dialog.
Open PortraitPro Studio, choose File and Settings, and make sure "Auto-Plugin Mode" is selected.
PortraitPro Studio is now set up as an external editor for your images. You can now select a picture in your library, right click and choose "Edit In" and then "Edit in PortraitProStudio".