Ok here we are! After the installation the first thing to do is the creation of your first mailing list, so:
- Go to Newsletter panel -> lists management
- Edit the mailing list created by default or use it for testing
- Set the sender address and create an html header + footer (take a look to newsletter template documentation)
You will have the mailing list with ID 1 so you just have to use the widget or simply insert the Sendit short code [ newsletter = 1] (with no whitespace!!)
I strongly recommend to test the plugin before sending newsletters. Try to subscribe and try to send the first newsletter to yourself!