In this itinerary you will find a complete panorama to know the Torres del Paine National Park in 4 full days.
You must consider a day of arrival and a day of departure.
My recommendation is that you stay inside the National Park or in a hotel in the surroundings, so that you can enjoy the surroundings of the park and its beautiful sunrises.
If you want to get to know Puerto Natales, you can add an overnight stay, where you can try local food, buy souvenirs and get to know this beautiful city in the south of the world.
It is thought of as a self-guided tour, you can rent a vehicle in Puerto Natales and I think it is much better to go at your own time. If for some reason you can't find it, all the hotels will be able to help you get tours per day.