I partitioned my 1TB external HDD into 4 parts. I use one to store files. I booted Kali Linux from my 16gb usb stick and installed kali on one of my external HDD partitions. The installation was successful but I cannot boot my PC from that partition of my external HDD; if i boot from usb, it skips and loads windows from my internal HDD. How do i boot from a that partition of my external HDD where kali is installed.
I'm assuming you've got Windows 10 on a current computer.
Boot to Windows.
Restart it, pressing shift when you issue the restart command and keep it pressed until a blue screen with further options show up.
Choose Use a Device, and your kali install should appear as a UEFI option.