What do you mean, "able it"? Enabled means turned on; disabled means turned off.
You can control the Flash Player plug-in in the Add-ons Manager (hold down Ctrl and Shift and press A to open it), Plugins category. It's labeled "Shockwave Flash"; you can set it to Never Activate to disable it, Always Activate to enable it, or Ask to Activate to have it initially disabled. If you've chosen the last option, you can turn it on by clicking the puzzle piece icon on the left side of the address bar or by clicking the blocked Flash content on the web page in question.

According to your system details, you somehow seem to have both the outdated and the current version of Flash Player installed. Try a little cleanup first:
1. Download the Flash Player uninstaller and save it somewhere handy, like the desktop.

• uninstall_flash_player.exe

2. Do the same with the Flash Player installer for Firefox. Also save the one for Internet Explorer if you use that browser.

• install_flash_player.exe (for Firefox)
• install_flash_player_ax.exe (for IE)

3. Close all applications.
4. Run the uninstaller.
5. Restart Windows.
6. Run the installer for Firefox.
7. (Optional) Run the installer for Internet Explorer.

Note that your System Details List shows multiple Flash plugins.

1. Shockwave Flash 12.0 r0
2. Shockwave Flash 11.9 r900

You can find the installation path of all plugins on the about:plugins page.

You can check the Flash player installation folder for multiple Flash player plugins and remove all (older) version(s) of the plugin (NPSWF32) and (re)install the latest Flash player.

• (32 bit Windows) C:\Windows\System32\Macromed\Flash\
• (64 bit Windows) C:\Windows\SysWOW64\Macromed\Flash\

You can get a possibly colored Lego icon on the left end of the location bar that indicates that Firefox is blocking a plugin.

• https://support.mozilla.org/kb/why-do-i-have-click-activate-plugins
• http://kb.mozillazine.org/Issues_related_to_plugins#Click_to_Play