Decals are a common way to add localized details to your textures. For humans, decals can be used to add e.g. tattoos, bruises and wounds, but decals can of course be equally well used on inanimate objects. You can add decals in DAZ Studio, but I never understood how it works, and for me it is much simpler to do it in Blender, especially if you want the decals to follow the mesh when animating. To make it easier to add decals directly in Blender, I made a new button called Make Decal, which is found towards the bottom of the Materials section.
The tattoo mesh also inherits the UV coordinates from the body mesh, but they are not suitable here since there is seam where we want to place the decal. In edit mode, clear all seams and then mark a new seam in a region where the decal will not cross, e.g. under the arm.
A freshly created material contains a principled node and an output node, which is good in our case. Turn down Alpha to zero. If the render engine is Eevee, we must change some material settings. Enable Backface Culling, set the Blend Mode to Alpha Clip or Alpha Hash, and turn off shadows by setting Shadow Mode to None