First of all you have to start by installing your Linux distro and next install and configure Squid.
Seriously, there are so many step-by-step guide out there on the internet that I doubt anyone here will provide you with another one. Check out and read various examples on the following sites.
The Squid site
The three above should get you up and running pretty fast once you have Linux installed. Of course when you encounter any problem with installing and/or configuring after you started you can post them here and someone will help you real fast.