I advise that accounts do not use AOL, Hotmail, aim etc., and instead use an account like Gmail
Setup another contact email account in AOL
Once you have logged in, click on the Options dropdown menu (visible in the top right corner of every page on AOL.com, and AOL Mail!) - select "Account Info" from the dropdown:
The next screen will open in a new browser window / tab, so make sure that your popup blocker doesn't prevent it from opening (tip for Internet Explorer: if you hold both the Ctrl and Alt keys on your keyboard while clicking a link, it will bypass your popup blocker!)
Verify your identity
For security reasons AOL will first confirm your identity by asking you to enter your password, and answering your security question. Then, you'll land in your Account screen: scroll down past the second section ("Account Recovery Information"), until you see the "Alternate Email" field: click on the link on the right - when you've already added an address in the past, it reads "Edit"
Type the full email address you want to add (username, "@" symbol, and domain), and click Save. This will automatically generate a verification email, sent to the address you just entered: it can be it can be any email address you own or have access to, and doesn't have to be another @aol.com / @aim.com email address.
Confirm ownership of your alternate account
AOL won't ever use this alternate account until you've verified that you own it, by clicking on the confirmation link sent to it. Check that account's inbox: a message from AOL Account Services, titled "Verify your alternate email address for AOL". It should have arrived within a few seconds: if you don't see it, check your spam folder, and/or click on the "Send again" link to get a new one.
If you waited too long before clicking on the confirmation link, you'll have to start the process over. Otherwise, you'll get the "Your alternate email has been verified. You can now use [email] to recover your account" confirmation screen. Next time you load your AOL Account screen, you'll see your account as verified, so you'll be able to use it to get an account recovery link if you ever forget your password!
Remove an alternate email address from AOL account
Since AOL only lets you change your alternate email account, but not delete it, your only choice is to click on the Edit link, and enter a obviously fake email address: you won't be able to confirm it, so it will stay permanently "unverified", but at least you'll have taken your original secondary email off the your AOL account