How do I reintsall the operating system from an external drive

SuzB wrote:

I have an Early 2015 MacBook Pro Core i5 that was completely wiped clean. I need to reinstall the operating system, but I can't get passed the "Transfer Information to This Mac".

https://discussions.apple.com/content/attachment/4b1f6d05-2695-48a1-b3ab-ab8eaf144e1e

I downloaded Big Sur onto an external hard drive from a newer mac and tried connecting that external drive to the 2015 macbook, but it is not recognizing the drive. The process i went through to do that was to 1) attached external drive to 2015 macbook, 2) turn on the macbook while holding down the option key.

Any suggestions on the best way to go about setting this up?

Thanks!!

Did you make that external drive bootable? as an installer.

Simply dragging and dropping the "install macOS Big Sur.app" to an external source is not enough.

How to create a bootable installer for macOS - Apple Support

Why not download Big Sur directly to the 2015 MBP to upgrade the macOS?

Big Sur macOS 11.2

https://support.apple.com/macos

or Boot to Recovery: How to reinstall macOS from macOS Recovery - https://support.apple.com/en-us/HT204904