That last image was not intended to be downloaded and used. that was just a screen shot from within the editor of the material. that’s why there is a white line at the bottom and top on your image.
You’ll need to find an image that you can create this effect from or make your own. You will want to make sure that it is capable of being masked so that you do not have the black area shown like in your image. Although I would argue that what you’ve created does look like a wicked portal, especially if you were to add some other effects around the edges!