In English "how to" is necessary, but in Portuguese it's optional (and avoided).
If you use it, you put a real ehmphasis on "how to".
- Você sabe como tocar? - Do you know how to play? - Do you know what you have to do in order to play? Do you know the right way of playing?
- Esse sabe como tocar um violão! - Now this man knows how to play the guitar