How do I put a cover image?

[Emcui]

Basically I can't make the post because it tells me that the cover image is not selected and I don't know what else "As indicated in our guidelines, a cover photo must be selected for new topics (threads) within the "Stars" sections and Starlets", "Social Networks", "NSFW" and "VIP."" ,

I already posted an image, but it still deletes me, so what do I have to do???