specified applying a manifest (closes #226)

index.html

@@ -730,6 +730,26 @@ <h3>
           </li>
         </ol>
       </section>
+      <section>
+        <h3 id="applying">
+          Applying the manifest
+        </h3>
+        <p>
+          A manifest is <dfn>applied</dfn> to a <a>top-level browsing
+          context</a>, meaning that the members of the manifest are affecting
+          the presentation or behavior of a browsing context.
+        </p>
+        <p>
+          A browsing context that has a manifest applied to it is an referred
+          to as <dfn>application context</dfn>. When an <a>application
+          context</a> is created, its session history is empty.
+        </p>
+        <p>
+          The appropriate time to apply a manifest is when the <a>application
+          context</a> is created and before navigation to the <a>start URL</a>
+          begins.
+        </p>
+      </section>
       <section id="updating">
         <h3>
           Updating the manifest