How do I install mootools?

[Kotsolis]

I want to install some plugins but I need mootools. How can I install them from admin panel?

[Kotsolis]

I've followed all the instructions here:
http://tutorials.yootheme.com/index.php ... 8&Itemid=2

So, I've edited the code and then tried to replace index.php with the edited file but I received an error message in my FTP:

550 index.php: Permission denied.

After that, I tried to rename FTP's index.php file but again nothing happened. Finally, I tried the last solution, editing .gz file's index.php and putting the one I've created but still nothing!

Can someone tell me how to install mootools?

[Kotsolis]

Finally I've managed to upload template's index.php with the correcton

// no direct access
defined('_JEXEC') or die('Restricted access');
JHTML::_('behavior.mootools');

But mootools were not installed. I've even tried to upload mootools.js (even if I have Joomla 1.5) so everything should be ok but it's not. As the above link says, I don't have anything else to edit. As the document says, I've tried to use View/Source on index.php and the code below does not exist (so obviously mootools are not installed):
<script language="javascript" src="http://www.yourdomain.com/templates/you ... se-1.11.js" type="text/javascript"></script>

Edit:
HAS ANYONE EVER INSTALLED MOOTOOLS OR AM I THE ONLY ONE IN THE UNIVERSE?
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