There are may buses you can take from El Calafate into the national park of Torres del Paine but it depends on what exactly you want to do there. Are you wanting to stay for a few days and maybe do some walks? Or just kind of pass through it just to see it?
If you want to stay for a while I highly reccommend staying in the Eco Camp, it is like a luxury campsite in a stunning location with a view to the famous spirals of Torres del Paine. If you want to know more just let me know and I will be happ to help :) about 8 years ago