Click the Mail > Accounts option at the top. Select the email account you want to log out from on...

Open GarageBand from your Applications folder (or download from the App Store) Let any sounds and...

First, turn off your Mac (Apple Logo > Shut Down). Now, Turn on again, holding down these keys...

In the Safari app on your Mac, choose History > Clear History, then click the pop-up menu. Choose...

Choose Apple menu  > About This Mac. This opens an overview of your Mac, including your Mac model...

From the Apple menu, select App Store. When the App Store opens, search for and download El Capitan...