Trace out the shapes you want to inlay onto a sheet of tracing paper.
Cut out the shapes carefully, following the outline with an X-acto knife.
Trace the paper cutout onto your 1/8-inch-thick brass plate.
Cut along the outline drawn onto the brass plate, on a scroll saw fit with a bi-metal blade. Brass is soft enough to cut with a typical scroll saw.
File the edges smooth of any burrs created by the scroll saw with a fine-grit file.
Trace the brass cutouts onto the surface of the material you wish to inlay it, then cut it out with a dremel or other router tool and press-fit with some epoxy.