Flash is said to be on its way out. That may be the case, however, I still need it. Currently Adobe is supporting thet NPAPI Flashplayer plugin and these directions are not really necessary. Just in case, there is a need to use the PPAPI here is how you can set it up.
Graphic User Interface Method
Set up the Packman repository following these instructions.
Open up the Software Manager from YaST

Search for and select:
- freshplayerplugin
- chromium-pepper-flash
Select Accept
Restart Firefox and you’re done.

Terminal Install Method
Open a terminal like konsole.
This can be done by pressing Alt+F2 and typing in either “terminal” or “konsole”
Add the Packman Repository
openSUSE Leap 42.3 Instructions
Latest Stable Release
sudo zypper –gpg-auto-import-keys ar -f http://ftp.gwdg.de/pub/linux/misc/packman/suse/openSUSE_Leap_42.3/ Packman
openSUSE Leap 42.2 Instructions
Previous Stable Release (has reached end of life)
sudo zypper –gpg-auto-import-keys ar -f http://ftp.gwdg.de/pub/linux/misc/packman/suse/openSUSE_Leap_42.2/ Packman
openSUSE Tumbleweed Instructions
sudo zypper –gpg-auto-import-keys ar -f http://ftp.gwdg.de/pub/linux/misc/packman/suse/openSUSE_Tumbleweed/ Packman
Add the necessary packages
sudo zypper in freshplayerplugin chromium-pepper-flash
Restart Firefox and you’re done.