MVC5 EF6 CRUD - WHERE Clause?

I created a basic CRUD web app using the database-first method, and I have the controllers generated. I need to be able to select a result in one Index view and have it return only the related results from another table. A WHERE clause applied to the Index based on the selected ID would do, but how would I go about implementing this?
This is the generated code select the Index results:
// GET: project_builds        public ActionResult Index()        {            var project_builds = db.project_builds                .Include(p => p.builds)                .Include(p => p.projects);          &nb ...