How to Install jQuery
There are two ways to use jQuery, either downloaded locally or on a Content Delivery Network (CDN). The local copy is just that, a file that sits within your document root on your server's hard drive. A CDN-hosted version means that the jQuery file sits on someone else's server and you just reference it in your code.
Whether you use a local copy of a CDN is up to you. For production websites, use a local copy of jQuery for speed and reliability. However, in development, it's okay to use the CDN version of jQuery.
Install jQuery locally
In other cases, you'll simply be prompted to download a file. In the end, you want to end up with a file named like jquery-1.8.1.min.js, regardless of whether you save the file or download it.
The file should be placed into your document root. Remember the filename; you'll need it later.
That's all there is to installing jQuery — download it and put the file into your document root.
Use CDN-hosted jQuery
The CDN-hosted option for jQuery is great for development. You don't have to worry about downloading the file or putting it in the right place; it's always available (as long as the CDN is up). CDN-hosted versions are available from many of the big-time players on the web, like Google and Microsoft.
You don't need to download anything in order to use a CDN-hosted jQuery, so this section is short and sweet. You can find the links for the CDN-hosted versions at www.jquery.com/download.