Make sure all firefox windows are closed
Press Alt and F2
Type YaST or yast2 and press ENTER
Key in your root password and press ENTER
Click on software management
Search for flash
Mark flash-player for uninstallation and click Accept
Close YaST
Visit
and click on the dropdown list to select the version for download. Select the .rpm version and download it
After you have downloaded it, close all firefox windows. Then right click on the rpm and select Open With->Install software
Key in your root password and press ENTER, it will install in a jiffy, as if nothing has happened 
Now Press Alt and F2, and type konsole or gnome-terminal and press ENTER
Type
sudo cp /usr/lib/flash-plugin/libflashplayer.so /usr/lib/browser-plugins/
and press ENTER
You’re done !