As the computer restarts, hold down the Command (⌘) – Option (⌥) – R combination immediately upon hearing the startup chime.

Hold the keys until the animated globe appears on the screen. “Starting Internet Recovery,” the message reads. ”This may take a while.”

A Wi-Fi menu appears. Internet Recovery needs an Internet connection to load the recovery tools from Apple’s servers. Click the menu to display the available Wi-Fi networks, and then select one to connect to.

Tip: If you’re connected to the Internet using Ethernet, you don’t have to connect to a Wi-Fi network during Internet Recovery.

If this isn’t an open Wi-Fi network, you’ll be asked to type in your password. Press Enter on the keyboard or click the checkmark symbol to continue.

After your Mac has connected to the Wi-Fi network, it’ll download a recovery system image from Apple’s servers and start from it, giving you access to the recovery tools.

This may take anywhere from a couple of minutes to up to an hour, or longer.

Choose the option Install OS X