Make sure your application/blocks folder has read and write permissions (i.e. 0777 rights). You can either do this in your admin/cPanel or via your FTP application (FileZilla or something else). When using this package on your localhost (WAMP/XAMPP/LAMP) it should usually work instantly!
As a default icon gets included with each every block you create (without uploading your own icon), give read/write permissions to the packages/block_designer/img folder aswell to be able to copy and move this file to the newly created block type.