PHOTO TRANSMISSION
The Nikon D750 is not compatible with the WT5 neither WT4 but has received a built-in WIFI chip.
This Built-in Wifi does not allow the FTP transfers. It allows a smartphone to browse your camera's SD card and potentially select a picture to download to the phone.
From there you can upload your picture to an FTP server (or via mail but it is not very effective)
Install Nikon Wireless Mobile Utility (free)
Install FTP-LUTIN (free) and set it as below.
Switch the Wifi on, on your camera (video tutorial)
connect your smartphone to this wifi network.
Launch NWMU
Choose "view photo" tick your pictures. Press "Download"
Launch FTP-Lutin
Choose the FTP Host you have set "prism event"
Press the icon, to browse the Camera roll, tick your picture(s), then press OK. That's it.
If you need to edit and caption the pictures before uploading it, you can try to use FilterStorm Neue (3€)