mario, well first make sure the sheet rock is in good shape, replace all bad sheet rock with blue sheet rock, i use wonder board a concrete type of board used around tubs showers,etc. tape and spackle all seams. make sure every thing is clean and dry. use only the glue suggested by the manufacture.and use a 4' level.use a hole saw to cut out you holes for the faucet.good luck on your project.