Sorry so stupid...
Well, not stupid really, just ignorant...
I downloaded octopi 0.15.1, edited the lines for wpa and country, and ran it on a Pi 3B+. I hooked up a keyboard and mouse and monitor to the Pi and it told me the IP address at the end of the boot process. When I checked my router's wifi list, it said octopi, so I kept following a tutorial and changed stuff until I was thoroughly confused. That was a week or so ago.
Today I was determined a couple of hours ago to get this working, so I tried to start over. I used etcher on the 0.15.1 zip file again and built a new flash drive, edited the wpa and country section of the octopi-wpa-supplicant.txt file (with notepad++) and rebooted the pi with the new flash. All was well at first: I logged into the pi with "pi" and "raspberry' and it liked that. Then I found the IP address on my router for "octopi" and put it into Chrome on my Win 10 PC, and the tutorial I was looking at said that at this point I should get a prompt for security, but just got "Please Log In" and nothing I try works.
I thought starting from scratch would reset everything but obviously it didn't. I'm so new at Octopi/Octoprint that I don't even know where to look to get it back to a new state. One tutorial says to put in a new userid/password at the prompt on the Pi, and another says to do it at the prompt at the octopi setup menu, and another shows a popup to secure my IP address when I first put in the IP in a browser. So, are these all going to be the same userID and password, or are there two, or three? I'm over my head here, and any help would be appreciated. Thanks in advance.