iOS Open new view from actual view

You need to make a connection to that view in Xcode.

IBOutlet UIView *view2;

....

Then link that view to the actually view in Interface Builder. You can then add it just like you added view1.

[view1 removeFromSubview];
[mainView addSubView:view2];

Alternatively, if you have View1 and View2 in different .xib files, you'll need to either:
1. Load the views using the [NSBundle mainBundle] object or
2. Creating a subclass of UIViewController to manage that particular .xib, then instantiate the UIViewController using initWithNibNamed:bundle: The class of the "File's Owner" in that .xib would be the same as your subclass of UIViewController. To get the view to load as a subview, you'd hook the view to the File's Owner (your UIViewController), and then (in code) do:

Personally, I prefer the second method as I understand what it's doing a bit better.

HTH,

Dave