@dsk
The application process, requirements, etc., differ for different universities. But, some basic criteria you need to fulfill include:
MBA in the USA

4 years of undergrad education from a recognized institution 720-730 score in GMAT 3 – 6 years of work experience TOEFL or IELTS A competitive CGPA in your previous degree will give
you an added advantage

MBA in the UK

3 years of undergrad education from a recognized institution 680-690 score in GMAT 2 – 4 years of work experience TOEFL or IELTS scores

I'd suggest you research the universities first and check the eligibility. This will give you an idea of what all do you need for pursuing an MBA abroad.
You can read about some top universities for MBA in the USA here: MBA in USA
Read about top universities for MBA in the UK here: MBA in UK