We're not a good place to get answers in a hurry. Since we don't get paid, people show up if and when it is convenient, rather than on a fixed schedule.
This isn't really a JSF problem, it's an IDE problem. The short answer is that the HttpServlet class isn't on the build path because you didn't setup your project to include it on your build path.
Eclipse does not come with a built-in J2EE server or J2EE libraries. You have to add them to Eclipse according to whatever server type(s) you are planning to work with - Tomcat, JBoss/WildFly, WebSphere, or whatever. The HttpServlet class will come included with that server and you must configure your project to reference it.
An IDE is no substitute for an Intelligent Developer.