If you want to upgrade your old Flash player to the developer Preview (2) release of Adobe® Flash® Player “Square” here’s how you can do it.
This requires that you already have the Flash player plugin 1.0-1. If you don’t, you’ll find instructions in the unofficial Fedora FAQ.

Now, you’ll going to need to download Flash Player Square.
Direct link to the 32-bit version: http://download.macromedia.com/pub/labs/flashplayer10/flashplayer_square_p2_32bit_linux_092710.tar.gz
Direct link to the 64-bit version: http://download.macromedia.com/pub/labs/flashplayer10/flashplayer_square_p2_64bit_linux_092710.tar.gz

When you have downloaded it, you’ll need to extract the “libflashplayer.so” file to a temporary folder (to put it where it really needs to go requires root).

Now, open up a terminal, go root:
[jk@fedora14 ~]$ su –
Password: yoursuperstrongrootpassord
[root@fedora14 ~]#

Now you move to the folder where you extracted the file called “libflashplayer.so” so you can move it to your pluginsfolder in Firefox (or other browser).
In my case I put it in my Documents/Adobe folder, and my pluginfolder is in /usr/lib/mozilla/plugins.
[root@fedora14 ~]# cd ..
[root@fedora14 /]# cd home/jk/Documents/Adobe
[root@fedora14 Adobe]# cp -pr libflashplayer.so /usr/lib/mozilla/plugins/
[root@fedora14 Adobe]#

Now, restart Firefox and open a 1080p YouTube video or something other in Flash In my case it was a lot better than 1080p YouTube video when I had the 10.1 version.

Remember, as Adobe says, you will have to manually update Flash when you have this preview installed.