To Purue undergrduate courses in abroad after 12th, you have to write standardised tests like SAT for USA, Canada and some universities in UK. and ACT for admissions in USA. You can choose any one of the both depends on location you want to study. After this test you have to write TOEFL  or IELTS or PTE these tests are required to test your English language skill. After that you have to apply for universities depending on your scores they will call you if necessary they will take you a short interview and then they will send you result.

Selection procedure is different for different universities in different locations.

For more information refer this links

www.colluni.com

https://www.hotcoursesabroad.com/india/

All the best!