Ouch...
Ok, I'll start with the basics :
_ a patch is a specific code created to replace another specific code in order to change a program functions (here, you need a patch in order to have your game work on your PAL DC)
_ a ppf file only contains (+/-) the code to change and the place to put it. You need to "apply" it to the image it was made for. So, you need to find "ppf-o-matic" or another patch applier and then patch your image (look on DC Copy World : you'll find these tools).
_ an image is a big file that contains what's on a CD, plus some info. Here, you have a CDI file => a DiscJuggler image.
_ 1st_read.bin file is the very first file that is read on a DC CD (I pass details...). To find it, look a the CD you burnt and that doesn't work on your PAL DC. You should find it with windows explorer in the root directory.
To patch your game :
1) find PPF-O-Matic on DC Copy World
http://www.megagames.com/dc/dc_ppf.shtml
2) laung PPF-O-Matic, open your ppf file, open your CDI file and apply your patch
3) burn your CDI file with DiscJuggler
I hope it will help you.