not able to install windows 10 from bootable DVD

Hello everyone,

I have a MacBook Pro 13' (mid-2012), Intel i7 2.9 GHz, 8 GB RAM and 750 internal Hard disk, running on High Sierra. I have installed windows 10 on to my external HDD (Seagate 1TB). I updated all the drives from bootcamp, all the drivers are working except the audio driver. So I reinstalled bootcamp again to Windows 10, but still no sound.

After reading few discussions here, I found that I should install windows through BIOS or bootable DVD. Hence, I erased my external HDD using 'disk utility' and GUID partition. I installed parallels to run windows 10 on my mac and formatted external HDD to NTFS. I burned ISO file into a DVD.

I restarted my mac holding key (alt) but I don't see DVD bootable disk.

can anyone help me to install windows 10 on to my external HDD.

Regards,

Zuko