Process:
1) Download PHPMailer from google code or github
2) Extract to folder within you php project and rename it to phpmailer
3) Create gmail-sample.php and paste the code.
4) Send mail from browser (e.g. http://localhost/your-project/gmail-sample.php).

Code (gmail-sample.php): 



    require("phpmailer/class.phpmailer.php");
    $mailer = new PHPMailer();
    
    /**** Email configuration***/
    $mailer->Username = "your.username@gmail.com"; // your GMail username
    $mailer->Password = "your-gmail-password";  // your GMail password
    $mailer->AddAddress("example@domain.com"); // recipients email address
    $mailer->FromName = "your name"; // readable name

    $mailer->Subject = "Subject title";
    $mailer->Body    = "Here is the message you want to send to your friend."; 

    /***Email Host configuration***/
    $mailer->Host = "ssl://smtp.gmail.com"; // GMail host
    $mailer->Port = 465; //GMail SMTP port
    $mailer->IsSMTP(); // use SMTP
    $mailer->SMTPAuth = true; // turn on SMTP authentication
    $mailer->From = $mail->Username;

    /***Send Email***/
    if(!$mailer ->Send())
        echo "Mailer Error: " . $mail->ErrorInfo;
    else
        echo "Message has been sent";