3D FlipBook - LARGE THUMBNAIL of the PDF

Hello

We are using the premium version of the 3D flipbook. We have been trying for some time now to put a LARGE THUMBNAIL of the PDF but finding it difficult. In fact, everything we have done so far has failed. We can see taht you are using a large thumbnail on your demo site. Can you pls provide clear instructions on how we can do the same?

We have already tried changing the thumbnail size in Media in the WordPress dashboard - that did not help.

Our URL: https://magneticthought.com/christian-science/

We look forward to hearing from you,

Regards

Mo Thomas