To use projection mapping, you will need a 3D model, a texture or an image to project, and a camera or light source as the projector. Additionally, you need a software that supports projection mapping such as Blender, Maya, 3ds Max, or Substance Painter. The basic steps are to import or create your 3D model and assign a material to it, then import or create your texture or image and adjust its size and resolution. Next, create a camera or light source and position it in front of the model, facing the area you want to project the image. After that, add a projection node or projection map modifier to the material settings and connect it to the diffuse or base color input. Finally, select the camera or light source as the projection source and choose the texture or image as the projection map. You can then adjust the projection parameters such as angle, distance, scale, offset, or blend mode to fit the image to the model.