How do I perspective warp the text correctly to the ribbon of paper?

Chuck/s method works well, but I'll offer up a different approach, but it has the disadvantage that you can't use Smart Objects so it is not possible to edit the text.

Make your white rectangle and type layers and merge them.  

Drag out a couple of guides to divide the rectangle into three.

Use the rectangle mmarquee tool to select each segment in turn, and copy to a new layer.  I have named them left, right, and centre for convenience.

Group those three layers as below.

Make the three new layers Smart Objects. THIS STEP IS CRUCIAL.

Select the group and use free transform to rotate all three layers.

Open the group and select the Centre layer, and use the Ctrl T shortcut to start Free Transform.  Because you made the layers Smart Objects, the bound box will have remained tight to the object, so hold down Ctrl (Cmd) and drag the centre left handle to drag down that side of the centre rectangle as below.

Select the left layer. Use the Move tool to align the right side with the centre layer, and use Free Transform and drag  the left centre handle into position.

Add the shadow and you are done