Mark car’s center line front and rear, and mark carpet’s center line. With those landmarks you will be able to center the carpet quickly and accurately.
Use some spray adhesive on drive shaft tunnel, and along the sloped areas over rocker panels, and front along fire wall. With a warm carpet, you will be able to work out most of the wrinkles; the adhesive will keep it in place until it conforms to the car.
Use an awl or ice pick to locate seat bolt holes, cut a cross just big enough to allow seat bolt to pass through.