Hi @perlimpimpin,
I hope you are well today and thank you for your question.
You are using Activello theme and the code provided in the following topic is for Dazzling theme so don’t use that code.
https://colorlibsupport.com/t/images-in-slider-2/
To achieve that you can use pages in the slider instead of posts by using the custom child theme solution shared in the following topic.
https://colorlibsupport.com/t/using-pages-rather-than-posts-for-flexslider/#post-52391
Best Regards,
Movin