You can prove your reading comprehension by a variety of ways:
1.By taking the Accuplacer Exam.
Your score must qualif you  for English 101.  You can take the exam at Olympic College: https://www.olympic.edu/services/assessment-testing-services/accuplacer-assessment
There is abundance of free prep question sites you can access through Google to get prepared for the exam.
OR
2.You have already taken ENG 101 in college. Send your college transcript.
OR
3. You can have an AA or a BA college degree.