My Dad taught me how to establish credit when I was a young married, with out a clue.
Step #1. Save the money (in full) for the item you want to buy
Step #2. Buy it on credit fr the best interest terms you can negotiate.
Step# 3. Make all payments on time until paid in full.
Rinse and repeat.
Bingo! You now have good credit.
This lesson worked well. We now pay cash and/or pay off our credit cards in full each month. Don't care if we have credit or not..we're on a cash basis. If we don't have the cash we don't buy it. Including cars, which we buy used. Our only new car was a 1969 Fiat 850 Spyder which we bought for cash with wedding gift cash. Cost us $2000.