Help with feature Images on front page and post/articles

Hello,

I need some help with featured Images on front page and post/articles. We have an old WordPress site that was recently updated. In the past we would just add 1 image directly onto the post/article. We love the Pinboard theme but it’s become time consuming to look up the images in each post and set them as featured images. Is there a workaround to just have the featured image on the front page display previously used images on older posts?

Thanks in advance and thank you for Pinboard its been the perfect theme for us!