For use in Firefox:
Go to http://www.adobe.com/go/getflashplayer
Under "Select version to download..." pick ".tar.gz for Linux"
Click "Agree and install now"
Select "Save File" (at some point I hope journal integration will occur here)
Close the download manager window when the download is complete with Ctrl-W (erk)
Exit Firefox (File->Quit, then "Quit" button)
Open the Terminal activity.
At the prompt, type: ~/Activities/Firefox*/install-flash
Type 'y' and press enter when requested, then 'n' to decline further installations.