Before you begin, there are few things you have to do:

1. You must know the email address that is associated with the fax number you wish to use.
2. You must request Send As permissions to be able to send an email on behalf of the share email address. Please see How To Request Send As Permission for a Shared Mailbox .
3. You must add the shared email address to your Outlook.  Please see Outlook | Adding a Shared Mailbox to Microsoft Outlook

After all the requirements are met, sending a fax is a very simple process. 

1. Compose a new email message and select the shared email address as the From address.
2. In the To field, type phonenumber@efaxsendsecure.com. 
   The phone number you are faxing to must always include the 1 and area code with the number. 
   For example, to send a fax to the phone number 920-555-1212 you would enter in the To field:  19205551212@efaxsendsecure.com
3. Attach a PDF or Word document that you want to fax.
4. Fill in the subject line and email body with any information you want to appear on the cover page.  If you do not want your regular email signature to show up on the fax, be sure to remove it!
5. Click send!  You will receive a confirmation email that the fax was successful in your shared inbox.