Thanks in advance for any assistance!

I recently purchased the Office 365 subscription that allows 1 user on 5 devices. I installed OK on one of my computers. Tried to install on my second laptop - asked for my account user name and password. OK, entered them the way I wrote them down for record, but says doesn't recognize. Maybe I fat-fingered my email address as the user ID, or maybe my password, but they're not working now. Is there any way to clear this up so I can install on second computer without knowing these?
(I have my key, of course, but says "already used")

Thanks!