How I can export a session of NP3 to my iPhone 6s?
All of the Neuro-Programmer versions are capable of exporting the content to MP3, OGG or WAV. It's recommended to avoid OGG or WAV files since they required additional codecs. Export the content as MP3, then use iTunes and add it to your iPhone 6s through Music synchronization.
You can check for this information using the following link: http://www.transparentcorp.com/products/np/faq.php