ok, looks like this is your first lesson on how to use a linux console.
First of all, obviously, open a terminal window.
Your first lesson in navigating within a terminal is the cd command - this allows you to move to different directories (or "folders" if you like) within file systems.
Type the following command:
this should take you to your home directory. the "~" symbol is used as a shorthand for "/home/your_user_name/"
If this fails, type cd /home/your_user_name
You now should be within your home directory.
now type cd desktop or cd Desktop - remember, Linux is case sensitive.... "desktop" and "Desktop" are completely different due to the capital or lower case "d". I use SUSE - it uses a capital "d" for the desktop directory.... other distributions such as Ubuntu may use a lower case "d".
Now, you need to know the name of the directory you extracted the files to. You can look at your desktop, or type dir which will show you all the files and directories within the current location.
Once you know the name, type cd flash_directory_name.
This should now have you in the appropriate directory and ready to type ./flashplayer-installer
Note that all the above cd commands can be merged into one line:
Hope this helps you somewhat... if you have any troubles, post a reply back and I'll be happy to help you more.