1) remove front and rear seats from car
2) remove coin tray and mount bracket, shifter handle and emergency brake boot
3) remove door sill plates
4) remove rear cargo side panels
now you are ready to install carpet
5) lay carpet out on flat surface in warm environment for a day or 2 to help remove folds and wrinkles
now would be a good time to cleanup any rust issues with floor and clean it up
6) lay new carpet in car, the warmer the environment the better, the warmer it is the better it will mold to floor shape
Recommend = cut nothing until you are sure, take your time and I would recommend you not cut the carpet by the door sill plates until you have reinstalled the front seats.