You have to build custom extension for this. This can not be done in one line code or one function. You can use fep_switch_{$switch} action hook to show send email button in this plugin menu and then again create a form to show input field for email address, title and content. Then when post that form you can use fep_posted_action_{$action} action hook to validate that form and send email with wp_mail function.

Regards
Shamim