I'm new to IOS development. I'm wanting to add to a new storyboard project that is a universal masterdetail a simple login control that is required before the user can go any further. that is, I always want them logged in. I'm using monotouch, but I don't think this question is monotouch specific.
Generally for login screens, I do the following:
ViewDidAppearof your root view controller, check if your user needs to login
PresentModalViewControllerto display your login screen modally
This should work for any type of controller you are using as the root controller.
There are certainly other approaches, but this one has always worked for me.