emery,

use thin layers of glue - very thin. Apply with a makeup wedge.

before applying the glue lay the pice on your head and line it all up. mark the front where the lace meets your forehead with your fingernail. the apply the glue using the nail impression as your guide. Once the piece is attached if there is any glue up fron of the lace try and clean it up with 99% on a q-tip.