If you are getting the message Are you sure you want to do this? when installing Lucille Music WordPress Theme, or any other WordPress theme, using the WordPress theme installer, most likely the web server is configured with low PHP settings.
Your web server is rejecting the upload due to the overall size of the installer .zip file. Please keep in mind that this is not a theme issue or bug, but a matter of server settings.
There are two ways to solve this:
1. Please send a support message to your hosting provider and ask them to increase your PHP limits so a larger zip file is allowed to be uploaded. They will know what has to be done in this case.
2. Install the theme via FTP.
The recommended limits for PHP are the following: