You have to enable developer mode and then turn on USB debugging.
Settings - System - About Device
Now find where it says build number and tap it 10 times.
After 10 times, go back to "System" and there will be an option for Developer Options, from there enable USB Debugging.
Now from here, connect your phone to your computer and an option on your phone should pop up stating what kind of connection you want between your phone and computer. MTP mode is enabled now.