how to enable or import bootstrap in child theme?

i am going to create a child theme for responsive classified theme version 8.1. Bringing core file in child theme ,lot of people are saying and even video guide is also telling us that do not bring core file in child theme. my question is that can we bring bootstrap to child theme ,if yes how the procedure and if successfully importing to child theme and in future if there is update regarding bootstrap, what will happen? does it effect to custom design and style which i modified in bootstrap files . What is the other best way to design a child theme with some thing look whole different . i will wait for your response guys if you get my point please reply on that topic and thank you in advance