Hard Drive lock in the re-instal process

Hi there,

I checked many forum and I can't fund an answer to my problem.

I did a reset of my Mc Sierra. After been to "Disk Utility", "Erase"(first partition on the top). Then I went back to "macOS Utilities" Press "Reinstall macOS", agree to the therms.

The first time I been there I had two hard drive, one was could not select it, and the second one "OS X Base System" could not selecting it "This Disk is locked".

Following some forum steps, but i wasn't able to unlock it.

What can I do?

Thank you for your help!

Christian