Simply include the JavaScript for jQuery before you include your own JavaScript:
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>
<script src="path/to/your/script.js"></script>
Though others have suggested simply copying and pasting jQuery into your own JavaScript file, it's really better to include jQuery separately from a canonical source as that will allow you to take advantage of the caching that your browser and intermediate servers have done for that file.