Asiye, you have a couple of options. If this is the case you can create your own AuthenticatingApplication and do something like this:
--- Case 1 ---
<?xml version="1.0" encoding="utf-8"?>
<lc:AuthenticatingApplication
xmlns:lc="http://www.adobe.com/2006/livecycle"
xmlns:mx="http://www.adobe.com/2006/mxml">
<lc:StartProcess width="100%" height="100%" session="{session}"/>
</lc:AuthenticatingApplication>
This will only display the StartProcess component after successful authentication. You probably want to add a container around the StartProcess component to make things a little more appealing.
--- Case 2 ---
If you want to continue to use the default Workspace code, you probably want to modify the WelcomePane, and remove the links to To Do and Tracking, as well you'll have to comment out the ability for the user to set their start page in Preferences to To Do and Tracking.
You'll want to modify the Workspace.mxml file and comment out the entries for ToDo and Tracking, and their model references.
<lc:WorkspaceModel id="model"
session="{session}"
startProcessModel="{startProcess.model}"
toDoModel="{toDo.model}" <--------------- remove that
trackingModel="{tracking.model}" <-------- remove that
workspaceNavigator="{tabNavigator}"/>
Recompile the workspace-runtime and you should be good.