How do I add/edit a featured image on a blog post?

I have created a new blog post, however i do not see any option to add the feautred image. The previous blog post has a featured image. I have no idea how i got it there. I am using word press with beaver builder. When I try to use beaver builder to edit the post with the featured image, so I can see where exactly the feautred image option is, I cant find the option. the featured image is not even selectable when using the beaver builder editor. I’ve tried using the customize button at the top of the blog post page but it doesn’t have any option for adding a feature image. I’ve spent hours and hours looking everywhere for this option to add the featured image and its driving me crazy, please help! thanks

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