I have a Bank of America credit card I can’t find the due date for the card on the app I only see the next closing date please help anyone I just got the card so I’m confused

Hello everyone I got approved for the Bank of America Unlimited Cash Rewards Visa Signature. My goal is to have an Amex platinum card. My question is: when should I apply for an Amex credit card? Because I got the Bank of America unlimited cash rewards visa signature today, how long from today should I apply for a credit card from American Express?

I’m 21 years old student never had a credit card I want one but don’t know which credit I should apply for I want to get to the American Express platinum as soon as I can thank you