Watney and his crew (Lewis, Johanssen, Beck, Vogel, and Martinez - they go by their last names) go out to space to go discover Mars. As they are in an emergency, and have to go back to Earth or else they will die, Watney gets blown away by a sand storm, the crew assumes he is dead, and he gets stuck on Mars.
Let's add wheels to drive to the Ares 4 landing site!
Mark Watney gets stuck on Mars, and is all alone.
Oh no! A dust storm! It's fine, let's keep going and use our excess saved battery in the MAV to get there!
Watney uses all his knowledge that he learned from NASA, and learns how to live on Mars. He travels to places to get certain things such as solar panels, and a radio that connects to Earth so he can communicate. However, the radio breaks as he is preparing for a mission to get saved by his crew.
Mark modifies the MAV (the space vehicle he uses to travel) for a long travel, and he starts his journey to the spot where he will get saved (Ares 4 landing spot - he was in the Ares 3 mission).
Mark Watney is close to the Ares 4 landing site, when he gets caught up in a very strong dust storm. He is using his solar panels for power, but when he is in the dust storm the sun is covered up and cannot give him power. He pushes through and keeps going, because if he doesn’t, he will miss the fly by of his crew, and he won’t get saved.
Watney makes it to the Ares 4 landing site in time, and the crew goes through a very complicated procedure to get him into the spacecraft to go back to Earth. Once they finish the procedure, they get him into the spacecraft, and help him with all his scars and give him some medication.