Once you've got your circuit built and tested, it's time to prepare your mask to install the electronics.
Depending on the type of mask you have, you may be able to skip or adapt some of these steps to suit the differences in your particular mask.
Widen eye holes
Trace the outline of the lens.
Cut about 1/4" inside the outline you've drawn, so the lens doesn't fall through.
Press lenses into eye socket, adjust size of hole as necessary using diagonal clippers.
Use a line of hot glue around the rim of the lens to hold it securely in place.
Add fishing line
Thread fishing line or string above and below eye socket.
This will hold the Hallowing in place tight against lens.
Cut a hole for the 10mm red LED, snipping through the back of the nose.
Insert the LED through this hole.