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.
Smart Photo Editor Studio is usually located at "C:\Program Files\SmartPhotoEditor Studio\SmartPhotoEditor.exe" or if you have 64-bit Windows it might be in "C:\Program Files (x86)\SmartPhotoEditor Studio\SmartPhotoEditor.exe" depending on whether you installed the 32-bit or 64-bit download.
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 Smart Photo Editor Studio, choose File and Settings, and make sure "Auto Plugin Mode" is selected.
Smart Photo Editor 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 SmartPhotoEditorStudio".
