create a sketch on the surface that you want to have the silkscreen layer and either draw the image or project from another surface or sketch. Then extrude it up or down by 0.001 to be able to change the color and texture of it. If you extruded it as a solid you can use the sold to make it a part. You make it an assembly so that you can use different views for drawings. If all of your parts are created of of one original then you can use the origin as your constraint.