To add tattoos in Photoshop, start by opening your base image (like a photo of skin) and the tattoo design in separate layers. Place the tattoo layer above the skin layer, then adjust its size and position using the Transform tool (Ctrl+T or Cmd+T). Set the tattoo layer’s blending mode to “Multiply” or “Overlay” to help it blend naturally with the skin tone, and lower the opacity if needed for a more realistic effect. Next, use a layer mask to refine the edges, brushing away excess areas to make it conform to the skin’s contours. For extra realism, add subtle warping with the Warp tool (Edit > Transform > Warp) to match the body’s curves, and consider adding a slight shadow or texture layer to mimic ink settling into skin. Finish by tweaking colors and contrast to match the lighting of the base image.