In css there are classes and id's. Classes have a period, so it would look something like this in your css file -
.nav { }
ID's have a # sign so it would look like this -
#homelink { }
You can also string these different elements together to target a specific element, but your question the code within your html file should look something like the code below. That id will trigger the css element have listed. Replace 'www.link-to-your-page.com' with your link.