Mixed content problem

I’m getting a mixed content warning the moment I activate the theme (NewsPortal):

An image with an insecure url of “http://demo.mysterythemes.com/news-portal/wp-content/uploads/sites/8/2017/07/news-portal-ad-large.jpg” was loaded on line: 126 of https://radimo.online/.
This URL will need to be updated to use a secure URL for your padlock to return.
An image with an insecure url of “http://demo.mysterythemes.com/news-portal/wp-content/uploads/sites/8/2017/07/newsportal-ad.jpg” was loaded on line: 198 of https://radimo.online/.
This URL will need to be updated to use a secure URL for your padlock to return.

I tried removing the link from the dashboard but it doesn’t do the trick. Need SSL on my site but want to use your theme. How to fix this?

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