There are thousands of posts a day in this user-to-user forum; it is the busiest support forum on the Internet. So there’s no way anyone reading your post can have any idea what you have seen previously or what you have tried to resolve the problem.
I think you have an AOL email account, and you want to add it to the email app on the iPhone. If my guess is wrong please correct my assumption. To add an email account go to Settings/Passwords & Accounts and tap Add Account. Tap AOL and enter your AOL username and password. However, if you have 2 factor authentication on your AOL account you will first have to log on to AOL.com via the web and create an “application specific password” and use that password instead of your regular AOL password for the built-in email app on the iPhone. AOL has instructions in their help section on how to do that.
If you have already tried to add it once first delete the account by going to Settings/Passwords & Accounts, tapping on it, and tapping Delete. Then restart your phone (Restart your iPhone - Apple Support) and start over.
The alternative is to not use the built in email account. Instead go to the App Store and download the free AOL mail app and set it up. It knows all about 2 factor authentication for AOL.
For this forum if you don’t enter any text before hitting “post” the box will turn red. However, you can still enter your question and hit post even though it is red. That happens to me also sometimes when I’m in a hurry. Alternatively, you can hit Cancel and start over.