how do I send emails with my website template?

I've been trying to figure this out for a long time now. I already realized that the invitation feature doesn't work properly. I can't disable the sign up page and send invitations to people who I WANT to sign up. Why? Because the sign up page is disabled. (I don't understand that part) But I want to know how do I send personal business emails with my website template located in the email. I tried sending an email through my site email account but when I sent it, it was just plan text. I need to see my logo at the top. I've already inserted that code in the email template area in my admin area.  How do I send out specific email templates to certan email addresses?