There's actually a few different ways you can create a highlighted word(or words) on your site. Some involve the use of a plugin, others require you to add code to your site.

Plugins
Plugins slow your site down.

Code
Adding code to your theme's files can be difficult. It can also kill your site if you don't know what you're doing...and I don't know what I'm doing.

So I'm going to show you the easy way.