Navigate to Setup -> Configuration -> Email Configuration and select EMAIL SETUP
Option 1: Sendmail
To make use of this build in option, you need to specify the email address to sent email notifications to. You can set the email address under Setup -> User Management and then "Edit" the admin user and provide a valid Email address in the field.
Option 2: SMTP
You may choose to use your own SMTP server/s by completing the field as shown in the image below. Please ensure that you enter the correct details when configuring.