Which wiki tutorial were you following? In addition to the info on the DH Wiki IonCube Loader page, note that you will either have had to install your own PHP or make your own copy of php.ini available. (see the links on the IonCube Loader wiki page linked above.)
If you are referring here to the php.ini page, you just need to navigate to the appropriate directory where you have placed it in your custom installation, or your custom php.ini set-up, and edit it.
It's hard to guess where that might be until/unless we know exactly what you have done.