Can't install Zend Optimiser

[N_KtheAL_EN]

I'm having trouble with my PHP!

Its all very new to me, I don't even seem able to open and view my PHP files. They mention Zend Optimiser, see here > http://www.phpbuilder.com/board/showthread.php?s=&threadid=10290464

I'm trying to install Zend Optimizer as one bit in the file detailed on the link reads

This file was encoded by the <a href=\"http://www.zend.com/store/products/zend-encoder.php\">Zend Encoder</a> / <a href=\"http://www.zend.com/store/products/zend-safeguard-suite.php\">Zend SafeGuard Suite</a></p>\n";
print "<p>In order to run it, please install the freely available <a href=\"http://www.zend.com/store/products/zend-optimizer.php\">Zend Optimizer</a>, version 2.1.0 or later.</p>\n";

The install Wizard now says
"Your php.ini was not found in its default location. Please specify the location"

Where might I find that?
Is there any other php software i need?
Please help, I'm way out of my depth already!