Unless you have set up 2-step verification on the account, just use the normal account password. Otherwise, create an app password through the AOL website and use it instead in TB.

https://help.aol.com/articles/how-do-i-use-other-email-applications-to-send-and-receive-my-aol-mail

Sorry if I sound a bit dim but when trying to download Firefox Thunderbird for emails and it got to the section where you have to enter "Email and Your Password" I entered the details that I use to log-in to AOL but it wouldn't accept that information. I have downloaded Firefox for browsing and had to make a password for that, should I have used my Firefox password. Utterly confused, sorry not a techy.

Use the same password as you use to access the account on the AOL website, unless you have 2-step verification, as mentioned above.

Also, in the Account Security section on the AOL website, you may have to 'allow apps that use less secure sign in' to access the account through TB.

Many thanks. This is very helpful and answers my question. Is there anything to worry about if I use a less secure means.

You can read about 'less secure' in the Less Secure Apps section here as it pertains to gmail accounts. It's not that TB or any other email program is less secure, it just a way for AOL and Gmail to encourage users to access their accounts via the ad-serving websites.