The AOL website points to this link on the Apple site for iPad users:
https://support.apple.com/en-us/HT201320
The type of account should be set to 'IMAP', with the incoming mail server set to 'imap.aol.com'. (If you're required to give a port number, it's 993, with 'SSL' encryption enabled).
The outgoing mail server should be set to 'smtp.aol.com'. (If you're required to give the port number, it's 465, with 'SSL' encryption enabled).
Some email providers require you to only enter the bit before the @ symbol as your username, whereas others require you to enter your whole email address. I think that AOL falls into the latter category but you might need to try both ways of ding it.
BTW, I wouldn't touch AOL email with an infinite number of the proverbial bargepoles. Thee are far, far better alternatives, including Gmail and my own preferred service, GMX:
https://www.gmx.co.uk/