Measure the walls where the shower surround is to be installed. Write down the measurements on a piece of paper.
Lay the shower surround pieces on a pair of sawhorse. Use a pencil to transfer the wall measurements onto the surround pieces.
Cut the surround to size with a jigsaw. Work slowly so you do not chip the surround as you cut it. Use an electric sander to trim shower surrounds that only need slight modifications.
Install the shower surround per manufacturer directions.