To play Rune Legacy you MUST have the client.
To be able to download the client you must have WinRAR and you must have Java.
First go to the link here:
http://www.mediafire.com/download.php?u1xgl3mzzyl
Then click the 'Start Download' button and when prompted click open. Then you will see a file called Rune Legacy Client and drag that to your desktop.
Now open up the folder when its done transfering and open the file called 'run.bat' now when this opens be patient and wait for the client to load.
Once the client loaded click Login and type in any Username and Password. Then click login and then wait patiently while it logs you in.
For any support post in the correct, 'client support', section.