Turn off electricity at the house circuit box.
Remove the screws holding the old light to the wooden ceiling. Disconnect the wires above it and discard the light, leaving an exposed ceiling electrical box with one black, one white and one bare copper ground wire hanging from it.
Mount the installation bracket that came with your light, using the included screws to attach it to the electrical box.
Hook the copper ground wire to the green ground screw on the mounting bracket and tighten it.
Connect the black wire from the fixture to the black wire from the electrical box, twisting a wire cap over them both. Repeat for the white wires.
Lift the fixture to the ceiling, tucking the wire connections into the electrical box as you do. Align the screw holes on the light to the screw holes of the bracket. Insert the provided screws.
Run a thin bead of caulk around the base of the light, where it meets the wood ceiling, if necessary, to deal with gaps.
Turn on the electricity.