My IMac won’t install El Capitan

Hi there!

Try these steps from How to reinstall macOS - Apple Support.

1. Press and release the power button to turn on your Mac.
2. Immediately after releasing the power button, press and hold Option-Command-R.
3. Keep holding the keys until you see an Apple logo or spinning globe.
4. You might be asked to select a Wi-Fi network or attach a network cable. To select a Wi-Fi network, use the Wi-Fi menu  in the upper-right corner of the screen.
5. If you're asked to select a user you know the password for, select the user. Then click Next and enter that user's administrator password, which is the password they use to log in to the Mac.

Now, try to resintall macOS:

1. Select the option to reinstall macOS.
2. Click Continue, then follow the onscreen instructions.
   1. If the installer asks to unlock your disk, enter the password that you use to log in to your Mac.
   2. If the installer offers the choice between installing on Macintosh HD or Macintosh HD - Data, choose Macintosh HD.
   3. If the installer doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk first.
3. Allow installation to complete without putting your Mac to sleep or closing its lid. Your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time. 
4. When installation is complete, your Mac might start up to a setup assistant. Follow the steps in the setup assistant.

If you're selling, trading in, or giving away your Mac, quit the setup assistant without completing setup, then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.

-Jack

Thanks. Try Shift-Option-Command-R and Option-Command-R at startup. These different key combinations are very important and different than Command-R.

-Jack

So you see that screen, even when you shut down and restart holding Option-Command-R?

-Jack