Found the nice wiki on how to edit with SSH.
Did that "successfully", rebooted the RPi2 and won't even get the HDMI screen displaying. I assume I added something really bad to config.txt (I added a line "max_usb_current-=1", something I found in vintage 2014 posts about how to get more current to the RPi2 USB ports). Undaunted, I moved to the next paragraph in the wiki; how to edit the SD card on a PC to remove my change to config.txt (quoted below)
Editing by another PC
Remove the SD-card from your RPi, plug it into a Windows, Linux or MacOS based PC. In Windows, preferably edit the file with a text editor capable of saving text files in Unix-format, such as Notepad++ or Wordpad (not Notepad.exe).
Put the SD card in the PC and all I can find is the recovery partition....no directory /flash. How do I edit with a PC????
Thanks 4 ur help, obviously a noob.