How can I use a PNG with transparency as a button?

Hello
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I am trying to use a png file with transparency (basically a circle that fades out towards the center) as a button on my Canvas. I have tried and googled for a while now and I haven’t gotten any further.
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I have tried various ways, including making the image into a sprite and adding it to the button, but then it loses the transparency (even though in the import settings I checked the Alpha is Transparency option.
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I attached an image illustrating my problem… I will greatly appreciate any help!
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On Button Script Change Transition from color tint to Animation and animated its alpha to transparent with Trigger Parameter.

Ok I figured it out myself: I couldn’t use the texture on the Button because I imported it as a texture, not as a sprite. Once I changed the Import settings to Sprite/UI 2D it was no problem to add it as the button’s sprite.