I'm attaching a copy of the User's Guide for the Comprehensive Air Quality Model with Extensions. This user's guide had many examples for different applications.
Hope this would be helpful to you.
Professor Yehia Khalil, Yale University, USA
Fellow of the University of Oxford, United Kingdom
Guessing that you need more help than just here's the guide. :-) Can you give us more details on what you want to do with CAMx?
First you will want to download the latest version.
At the same time download the example files.
Go through the guide and be able to explain the input file for the examples (i.e know why they choose each option).
Assuming you want to run it for your country/region you will need (in CAMx format)
1: Meteorology files. For this you willl ned to install and run MM5 or WRF or some other prognostic 3D weather program
2: Emissions inventory for your region including industry and biogenics (google Alex Guenter Megan model biogenics)
3: Will also need to setup a Linux system to run and compile the code. I used Fedora 4 and the Intel Fortran Compilers (but that was about 8 years ago so check what is required now)
I'm sorry to say this but it's a steep learning curve ahead.