If you have a Mac of your own, you could download it onto a large capacity flash drive, and then copy it onto your friend’s Mac to install it. The installer itself doesn't need an Apple Id, but it may want you to sign into iCloud after installatio.

1. Os X El Capitan Download Without Apple Id; Apple Mac Os X El Capitan Free Download; Sep 30, 2015. Apple's Mac OS X El Capitan now available for download. The computer software makes common actions easier, such as letting users view two open windows at once with a split-view screen. The new OS from Mac is here in OS X El Capitan.
2. Once you’ve done that, here’s how to install, reinstall, or upgrade to El Capitan, step by step: Boot from your Recovery HD partition by restarting your Mac while holding down the Command+R keys. The OS X Utilities window appears. Select Reinstall OS X, and click Continue. The OS X El Capitan splash screen appears.
3. Jul 25, 2021 El Capitan Clean Install on Empty Volume with El Capitan Installer This is the easiest method for the clean install. Here, you can install the OS X El Capitan Installer onto an empty volume, or you can use a storage space that has the content which no longer needed and don’t mind removing.

Start up from macOS Recovery

Determine whether you're using a Mac with Apple silicon, then follow the appropriate steps:

Apple silicon

Turn on your Mac and continue to press and hold the power button until you see the startup options window. Click the gear icon labelled Options, then click Continue.

Intel processor

Make sure your Mac is connected to the Internet. Then turn on your Mac and immediately press and hold Command (⌘)-R until you see an Apple logo or other image.

If you're asked to select a user you know the password for, select the user, click Next and enter their administrator password.

Reinstall macOS

Select Reinstall macOS from the utilities window in macOS Recovery, then click Continue and follow the onscreen instructions.

App Store Download El Capitan

Follow these guidelines during installation:

• If the installer asks to unlock your disk, enter the password you use to log in to your Mac.
• If the installer can't see your disk or notifies you that it can't install macOS on your computer or volume, you may need to erase your disk first.
• If the installer offers you the choice between installing on Macintosh HD or Macintosh HD – Data, choose Macintosh HD.
• Allow installation to complete without putting your Mac to sleep or closing its lid. Your Mac may restart and show a progress bar several times, and the screen may be empty for minutes at a time.

When the installation is complete, your Mac may restart to a setup assistant. If you're selling, trading in or giving away your Mac, press Command-Q to quit the assistant without completing setup. Then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete the setup process.

Other macOS installation options

When you install macOS from Recovery, you get the current version of the most recently installed macOS, with some exceptions:

• On an Intel-based Mac: if you use Shift-Option-Command-R during startup, you'll be offered the macOS that came with your Mac, or the closest version that is still available. If you use Option-Command-R during startup, in most cases you'll be offered the latest macOS that is compatible with your Mac. Otherwise you'll be offered the macOS that came with your Mac, or the closest version that is still available.
• If the Mac logic board was just replaced, you may only be offered the latest macOS that is compatible with your Mac. If you've just erased your entire startup disk, you may only be offered the macOS that came with your Mac, or the closest version that is still available.

You can also use these methods to install macOS, if the macOS is compatible with your Mac:

Os X El Capitan Install

• Use the App Store to download and install the latest macOS.
• Use the App Store or a web browser to download and install an earlier macOS.
• Use a USB flash drive or other secondary volume to create a bootable installer.