warn on where to download the network (closes #370)

hyphe_frontend/app/views/export.html

@@ -17,7 +17,8 @@ <h1>
               EXPORT WEB ENTITIES
             </h1>
             <span class="md-subhead">
-              Pick a file format and download the list of <span hyphe-glossary="web entities"></span> and their attributes.
+              Pick a file format and download the list of <span hyphe-glossary="web entities"></span> and their attributes.<br/>
+              To download the network of links between the web entities, click NETWORK in the left menu, adjust the filters, then click on the download icon (<md-icon class="md-avatar material-icons" role="img" aria-label="file_download">file_download</md-icon>).
             </span>
           </div>
 
@@ -301,4 +302,4 @@ <h4 style="line-height: 1.3"> {{ field.type }} </h4>
       </div>
     </div>
   </div>
-</div>
+</div>