Installing Adobe Flash Player updates

Unable to install Flash Player update. Password doesn't work to allow me to proceed. The username that pops up in the Adobe box is not my Apple I.D. (which I use for iTunes and everything else) but rather a username requiring a password which Adobe describes as a separate one which is used for logging into my Mac machine. I never log into and out of my Mac so it's never been tested. That name (my actual name) also appears on my desktop, upper right corner, with my photo, set up when the Mac was new). To my knowledge I have only ever had one Apple password for the past 10 years. At some point late last year Apple required that I reset my password (for greater security) which I did in the Apple Store and it has worked with everything else. So, bottom line, my correct password does not work with either my Apple I.D. or my username to install the latest Flash Player update.