Help needed to install v10 Flashplayer

I read the othe post about flash in firefox, but that procedure doesn't work for me on later firefox, give erros.

And when I click on "click here to download the plugin" on a website that needs flash, firefox always says "No suitable plugins were found".

So how do I install the latest Adobe Flashplayer 10 ActiveX in the latest portable firefox please?

Thank you.