How to mark up this element?

I can not figure out how to make this square, I get it a semicircular5def8cc681c24008505395.jpeg
April 3rd 20 at 17:18
1 answer
April 3rd 20 at 17:20

I think I will be able to change by itself, if it's not mine, I found them in the screenshots.
8f572829be7fc4faf4b0ef68cb821ed9.jpg - Herta commented on April 3rd 20 at 17:23

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