Enable use of gadget on your MailUp admin console
In order to allow Blogger servers to call MailUp you have to disable restrictions on caller IP, that is enabled by default on "Settings" -> "Account settings" -> "Developer's corner" -> "Web services".
Gadget installation on your Blogger page
Follow the screenshot sequence (click on images to expand)
- Edit your Blogger page (Go to "Layout")
- Add a gadget to your sidebar
- Browse in gadget directory and add MailUp gadget by specifying an URL
- Proceed with gadget configuration