Replacing an area on a texture with a transparent texture

To make it clear what I’m trying to do. I am trying to implement the placement of a tattoo on a body area. Which way I went: there is a base texture, there is a texture with green circles which helps to find the desired area. Then I replace the green area with my tattu. The problem is that my tattoo has a transparent background, but in the shader I get a white background

You need to change your graph to transparent via the graph settings tab, and feed your Alpha values from your texture into the Alpha output.