Ubuntu installation problem - am I missing something?

This may be a stupid question, but I am by no means a techy.

I downloaded the ISO file for Ubuntu and put it on a usb drive using Rufus. I completed the installation, and then it asked me to restart my computer. I did so, and it launched back up to the black screen where you choose to try without installing, install, etc. I figured this was because the computer was still booting the flash drive, so I restarted it without the drive, and I get a black screen that says "Reboot and select proper boot device". I did select my hard drive, so I don't know what I'm doing wrong. Any help is greatly appreciated!

Since I did a clean install, this has rendered my computer useless until it's fixed, as I currently have no OS.