Upgrade Issues...

In my attempt to erase and reinstall High Sierra back into my late 2011 MacBook Pro, I've hit a snag. From Disk Utility I am to select the drive (out-dented entry) from the device list. However, what appears is the following: Internal displays Macintosh HD;

Disk Images: OS X Base System.

This will not work. On restart, the following message appears:

"macOS could not be installed.... Volume contains macOS or OS X Installation media.''

I'm thinking to download HighSierra and create a startup disk to proceed.. What can I do??