If you dont have a Custom Coldboot,

then your good to go, you dont need my guide,
To play PSX Isos you need two things.
1. Put your PSX game in your computer and with any ISO tool, convert it to ISO, just back up your game into ISO format.
2. When you get your ISO you must convert it into "eboot.pbp" You'll get two files, the eboot and the .bin file.
Then just place it in your 'game or game150" folderl ike any other homebrew and it will load under your game /memory stick.
To convert to eboot you need this software:
http://www.pspmod.com/forums/showthread.php?t=11619 (website for backgroundss???)
good luck!