Windows 10 updated, but opened a new log in page

[Esteban32696]

Windows 10 on Dell Inspiron 3650 desktop, almost new;

Normally, I turn computer on, log in window come up , & I type in my I use.

Kept getting pop-up to update Windows. Foolishly, I clicked on one. It updated, but now when log-in page shows up, it is for OUTLOOK, which I never use & don't remember password for. I cannot log in so I cannot do anything.[ I am using a tablet to do this ] . I was able to " Shift/restart & get into safe modes, etc, but none let me go set it back to how it was. I guess I need to get into " Start-Up page.
Please tell me how I can change this back !! THANK YOU !