Can't log-out to sign in for another account

Hello - I created a free account on Firefox when I was exploring the software and then made a different, paid account through a Chrome browser. But since it's better to use this with Firefox, I'm trying to login to my paid account through Firefox, but whenever I click "login" it takes me to my free account with no option to logout and sign-in under a different password. I can't even seem to find the login info in my Firefox keychain to delete.

Thanks in advance for your help,

Evan