I'm trying to figure out how to send a welcome email with

I'm trying to figure out how to send a welcome email with the relevant information that the member needs to go to the site and log in.

Currently, they're getting one directly through WordPress, I believe, that says simply:
Username: username
Password: password
http://mysite.org/wp-login.php

I would like to either be able to modify this email so that it read nicer (can I do that?) or get rid of it completely and have the membership plugin send out a welcome email.

I went into Membership >> Communications, and added on for "0 days after a subscription is paid" but I never received this email. This email also doesn't appear to have the password shortcode in it, either.

So, my question is: How do I send only 1 welcome email to my members, immediately after they sign up, with the relevant URL and login info (and a "thank you for signing up with us") message?

Thanks!