In order to send emails on your behalf, you'll need to enter in the your Gmail SMTP settings.
As part of Gmails requirement for allowing third party providers to send mail on your behalf, you will need to first allow your Gmail to be used by "less secured apps".
In order to do this, you will need to go to the following link: Allowing less secured apps.
Once on that page you may be required to login if you haven't already. Once you're logged in you will need to select the switch icon to allow apps to connect.