I am able to see my emails on Safari but I can not get them in Apple mail as I need a new password

When I go through Safari it now uses one password and I can get access to my emails. I want to use Apple mail as I find it easier to use but when I try to get my email there I get a message to enter my password. I try my old passwords but can't get Apple mail to work. I think that is because I changed to 1PW in Safari. I don't know the password now and I think 1 PW doesn't want to work in Apple Mail? how do I get 1PW to work in Apple mail. SorryI am not very computer literate.