Regarding An image with an insecure url

i recently purchased hotel master theme, and after i completed the website, it kept showing that the website is insecure, so i contacted my hosting and they have told me that there is an insecure image in the media, we both tried to locate the file, but failed to do so.
so eventually the host said that it could be in the scripts.
can anyone help me how to correct this.

you have to make sure your website is running with secure ssl (https) and you have made all necessary settings in website admin (wp-admin for wordpress site) to run on ssl (https). Thanks