I am pursuing B.Sc in computers and want to do PG from abroad in computer science. How should I go for it?

Since, you didn't mention any country of your choice, I am providing a guide of US as an example. For all the countries, the process remains the same, so you can get an idea form this guide. You can visit the below mentioned link for more information: https://studyabroad.shiksha.com/study-in-us-