1.) Download ISO.
First you should decide what architecture that the target machine has, things like 32b or 64b and so on. You can visit the elementary Information page to see a list of the minimum requirements needed by the distribution along with links to more information and the download page.
2.) Create Boot Media.
Depending on the age of your target machine you may have a few options on what kind of boot media you create from the ISO image that you have downloaded. A bootable CD/DVD is the most common method used when installing Linux, however you may be able to create a bootable USB thumb drive that will help speed up the install a bit.
3.) Install elementary.
Welcome, here you can choose your language and aether tryout elementary OS without installing any thing to your machine or if you feel that your ready to begin, click on the Install button.
4.) Preparing To Install.
You are given the option to download updates while you install, this will save some time afterwards but my slowdown the installation some, you also have the option to install some 3rd party software for imaging and video playback.
5.) Installation Type.
There are many options that are available in how you install your system, including full disk encryption. For this guide we will be using the full disk option as a single operating system.
Here is how the install will partition your hard drive, for systems with multiple hard drives, you need to be sure that the correct drive is chosen here, if you are unsure perhaps shutting down your machine and unplugging all but the one you wish to install, clicking Continue will erase the disk and any preexisting data will be lost.