Get XAMPP, MAMP, or another project that already has everything ready to use or hire an admin with PHP knowledge to prepare your server. There are a thousand ways to install and configure PHP and MySQL, and I’m sorry, but we are not a support community for learning how to do so. There are plenty of places on the web where you can get that information. Our requirements are pretty clearly listed in the post Ryan provided and folks are always willing to answer specific questions regarding specific environment problems or errors they are getting.
Did you consider
mod_security might be the problem as well?
MODX Staff