install linux
 

How to install linux OS? Please share step by step procedure in easy language.

It depends on which particular distribution you want to install, but a duckduckgo search for "how to install xxx linux" will give quite a few step by step tutorials.

If you have a SPECIFIC question, we can help...otherwise, you need to read the "Question Guidelines" link in my posting signature. There are THOUSANDS of how-to guides you can find with a Google search if you tried to look.

And you don't say WHICH "Linux OS" you want to load...if you're new, I'd suggest Mint. Once you go to their website, you might want to try reading THEIR installation instructions.

I'll second Mint, and they have a very nice guide:
http://www.linuxmint.com/documentation.php

If you are going to install alongside Windows (what we call double booting), defrag your Windows first. The installer will shrink the Windows partition for you, and probably more safely than Windows would. If you don't know what a partition is, read (skipping the complicated bits)
http://en.wikipedia.org/wiki/Disk_partitioning

How it install???

READ!!! the install instructions for the distro you are going to use

If it has one! Some don't, or they have one that's out-of-date, on a completely different site with no link, or that's well-nigh unreadable: one reason why I said Mint.