It's best to print the mask on thin card stock, if you have it, or heavy computer paper. After printing, cut carefully around the clown face.
With small scissors, cut out the two eye openings. Make two small slits on either side of the face, where shown by the " | " marks. Thread about 1-1/2" of elastic cord through the front of one of the slits. Double the elastic over on itself at the back and staple together. Leave enough elastic to go around your head, then thread the other end into the slit on the other side, double over and staple together as before to finish.