How important is publication for PhD admission?
I would say publications dont matter to start with a PhD, in general. Having them might help in reducing length of your PhD.

A good thing to have is liking for one area in CS, and good knowledge in that area atleast. e.g. systems or security or algorithms or formal verification or databases or distributed systems etc. Later when you join for the PhD program, you will do courses and talk with people to get an understanding on what is a good research problem etc.