Users with Sales access can access advertiser accounts and send emails to the contacts.
To send an email, first make sure that the contact you want to send the email to exists in the Contacts tab.
Then go to the Email tab and click the lower New button. This will bring up the Standard email form that was selected to be the default email template by your Administrator.
Enter a subject line and select the contact you want to send the email to.
Type up your message and click Save. The button says Save rather than Send because you can schedule the email to be sent at a different time. If you don't schedule it, your email will be forwarded to your email service provider for immediate delivery.