Hello Kev,
can give me description or screenshot of the error you get. so i can better understand.
And one more thing, about path, you can do this in two way.
1.. You can set Smarty class path by modifying php.ini file as done on webpage you have given.
include_path = ".;c:\wamp\bin\php\php5.3.0\pear;c:\wamp\bin\php\php5.3.0\Smarty\libs"
by doing this you just need to insert line of code like
"require_once(SMARTY_DIR . 'Smarty.class.php');"
Here SMARTY_DIR is constant, which automatically set by Smarty.
2.. second way is what i have done in my previous reply
In all cases you have to make path to smarty class file that's it..