Hard Drive Erase for computer sale

Hi All,

I need to erase my hard drive so that I can sell the computer. The instructions say to erase the Macintosh HD from the Disk Utility menu.

I can't select the Macintosh HD icon. It only allows me to select the APPLE HDD with a lot of number Media, underneath it says: SATA Internal Physical Disk - GUID Partition Map.

Beneath that icon is a "Container disk1" icon and then my Macintosh HD icon. Should I erase the APPLE HDD ... drive? Thanks for your help.