How do I make a bootable usb drive to download OS X Yosemite?

You really need use a USB flash drive or external hard drive. But you cannot just burn the image file. You need to follow the steps for a bootable installer. How to create a bootable installer for macOS - Apple Support. Otherwise, it just won't work.

I posted this already, but here it is. You need to have access to another real Mac, not Windows, that supports OS X El Capitan. We then need to download OS X El Capitan, How to get old versions of macOS - Apple Support, and make a bootable installer the right way, How to create a bootable installer for macOS - Apple Support. Do all this using a Mac.

So here is what we need to do. You need to have access to another real Mac, not Windows, that supports OS X El Capitan. We then need to download OS X El Capitan, How to get old versions of macOS - Apple Support, and make a bootable installer the right way, How to create a bootable installer for macOS - Apple Support.

You cannot just put a DMG file on a flash drive and boot from it. You need to create the bootable installer on an official Mac, that loads into Mac OS.

What exactly is your issue?

Hi Diego916,

No, you cannot make a bootable USB Drive in Recovery Mode. You need to be inside of macOS.

And I do not understand the second part of the question. If you are referring to a Windows OS from a PC, you cannot get macOS from Windows, and if you did, that is illegal, and most likely a fake version of macOS.

Cheers,

Jack

Yeah do not ever use "TransMac" or any other Windows Mac software.

What is the year of your iMac?

Just try the boot picker several times, try different USB ports, and make sure the USB was created using real Apple software.