At 51 I am a beginner at investing

I recently opened SoFi checking and savings accounts due to the high interest return yields and would like to start investing for retirement. I am 51 and I am learning on YouTube about investing for my passive income and future. I am hearing about compound interest savings accounts (NexBank 5.26 yield), a Vanguard Target date retirement fund or a S&P index fund. My employer does not offer 401 k. How would you balance these if I were to retire at 65? Thanks in advance!