The best ways I've seen that done are by 1) using flashbacks and 2) using a frame story.
https://www.google.com/search?q=writing+flashbacks&oq=writing+flashbacks&aqs=chrome..69i57.3588j0j7&sourceid=chrome&ie=UTF-8
https://www.google.com/search?q=frame+story&oq=frame+story&aqs=chrome..69i57.2601j0j7&sourceid=chrome&ie=UTF-8
How can I switch between different POVs (first person, third person) in my story without being too disruptive?
2 answers
Thank you. I think I might use first-person the most because I find it harder to convey the character's thinking in third-person, and it just feels more personal.