Problems with main photo

Hello, I have uploaded on my blog this new theme. I have a problem with the main photo. Theme need to have a preview photo – mandatory. Then, when I had another photo, as main photo on my article, apart from the one of preview, whani open as reader my article, the site duplicate them (that is to say I see the mian photo up and the preview one down). It is possble to insert a main photo without i see in the article also the preview one?
Thank you so much

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