For using Bootstrap you would have to download it and you can get it from http://getbootstrap.com/ , on unzipping the file you would get a folder with tha name of bootstrap. Copy and paste this folder to the location where you want to keep your files you would do all the stuff in this bootstrap folder that is so that you can use the functionality of bootstrap. Make a new file using a text editor such as notepad, notepad++, sublime any of which you are comfortable with.
If you dont know HTML coding you can get the code from different websites such as http://www.bootsnipp.com/ You can select different snippets to add to your website and copy and paste the code. If you try to understand the code it is very easy to get it. s At the starting of the text document you would have to enter this line
<!DOCTYPE html>
This <!DOCTYPE> declaration refers to a DTD, because HTML 4.01 was based on SGML, the DTD specifies the rules for the markup language, so that the browsers render the content correctly. HTML5 is not based on SGML, and therefore does not require a reference to a DTD.
To make your website link to the bootstrap functionality you have to enter the following lines in the HEAD tag of your file.
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link href = "css/bootstrap.css" rel="stylesheet">
<link href = "css/styles.css" rel="stylesheet">
To use the javascript you have to add these lines in the HEAD tag
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script src = "js/bootstrap.js"></script>
You can design the page as you desire. I designed a Login page for my website so that people can login to their twitter account so that they can access the website.