The majority of getting good at fighting games is theory and practice. Fighting games are split into 3 states: Neutral, advantage and disadvantage. The neutral states is where both players are in mid with neither players grounded with nobody having hit anyone. The advantage and disadvantage states occur when a player gets a hit or another player enters an otherwise disadvantaged position that the advantaged player can exploit.

1. Learn your character's bread and butter in neutral. What are their openers? What are their safe spacing and footsies tools?
2. When you've broken neutral, know your damage dealing combos.
3. Learn and practice your character against the whole cast, a lot. You can't win neutral without knowing how to play neutral against everyone and if you can't win neutral you can't do damage.
4. Spacing. Learn spacing. Spacing is the difference between getting really good and just being ok. Spacing is what enables you to punish opponents with big damage when they take unnecessary risks by baiting them into it.

All of these topics should have pretty in depth reading and learning if you ever want to go into and learn them. There should be videos going into all of these specific areas of fighting games if you google around for key terms.

Getting good beyond this basic level takes advanced theory, tech and character specific situational matchups. I don't recommend getting into tech or advanced content until getting the basics of neutral and punishing opponents though.