the motherboard I\O panel is where you would connect the display.
similar to this on the rear of the system:
.
depending on it's age; newer models will have HDMI, DisplayPort, possibly DVI ports.
older models will have VGA, HDMI, possibly DVI ports.
just compare the cable connector to the available ports visually and see which matches.
you can even google the types i mentioned just above and compare the images to the available ports.
but once you have connected the display here though you will not be able to output video through the GTX 1050 Ti or use the Nvidia proprietary DAZ Studio software.
you mean the default connection is VGA or the adapter?
i do not believe what you are hoping to achieve is possible with this setup.
like Eximo mentioned, you should be looking into getting a more capable system that is prepared to handle this type of software than trying to rig some sort of custom setup using this OEM Lenovo system.
adding a more advanced dedicated GPU with the necessary VRAM would most definitely mean that you will also need a more powerful power supply.
problem there is that these OEM systems are designed with proprietary hardware and it's unlikely you will find a retail power supply that can be paired with this system.