Best bet is to download the .BIO file, place it on a USB flash stick, insert in NUC and reboot. When splash screen appears, press F7 key, browse to the file and select. System will reboot and install BIOS update.
The Latest bios and all drivers for your NUC you can download here: Downloads for Intel® NUC Kit NUC7i7BNH
The bios update instructions see here: BIOS Update Instructions for Intel® NUC
Support for installation the Optane memory: Support and Installation of Intel® Optane™ Memory on Intel® NUC Kits
Hope this helps