The following is an instruction on how to install ENB.
Installing an ENB can be quite tricky, especially if it's your first time. Of course, there's always a first time for things, so this guide is should help you to get through the installation step by step. Note that you're still supposed to read through the description of certain pages, because not every ENB is installed in exactly the same way. Please read through the guide first before making rash steps and decisions. Some files should better be backed up before editing.
Where to find itEdit
First of all, you are to download the ENB itself from the official website. It can be found here: ENBdev. Download the latest version of the ENB. Then go to your download folder and extract the ENB package you find there. After extracting the ZIP-file, you'll see two folders, one called the Wrapper version and one called the Injector version. There isn't much difference between the two, but most people opt for the wrapper version. The injector version is said to be more performance friendly however, and is more often used when there are incompatibility issues with your system.
Which one to pickEdit
It is safe to assume that your computer will be compatible with the wrapper version, especially if you're using a Windows. Copy the files from the Wrapper version into the Skyrim root folder. This folder can be found in your Steam directory (where you installed Steam). Open the Steam folder, navigate through the SteamApps and then go to the 'common' folder. In this folder, you'll see all your installed Steam-games. Open the Skyrim folder and copy the files from the Wrapper version into this folder, not the data folder.
The ENB presetEdit
You have now installed the ENB program itself. To make it work, you'll also need an ENB. Look up the one you'd like to install. Quite a few can be found on the Skyrim Nexus. When you've found one to your liking, download the file and extract the archive as well. Generally, you'll have to just copy the ENB files from the archive you just extracted and copy it to your Skyrim root folder as well. This is not the same for every ENB, so make sure you read through the guide that the author of the ENB preset has written for you.
A few files should be backed up before adding or changing an ENB. These are the SkyrimPrefs.ini and the Skyrim.ini, as well as your savegames. Other than that, there should be plenty of youtube videos on the installation, as well as many guides that can help you.