Not exactly sure what you're trying, but you can add new 11x14 layer without affecting the 8x10 layer (original image) in any way.
Open the 8x10 image you have.
Menu: Layer->New Layer (Ctrl+Shft+N), in the dialog give it 11x14 size.
Menu: Image-> Fit Canvas to Layers. Now you'll see the 11x14, it was out of canvas boundaries.
In the Layers Toolbox, hide the upper layer using the eye icon. Activate Alignment Tool (Q).
Click on the canvas, you will see white small rectangles in the corners of the 8X10 layer.
Select "Relative to image" in the Alignment Tool drop-down, and use the buttons to center it.
Add the other stuff on the new layer. Note that text created with text tool, will automatically be on a new layer.
You can create 22x14 layer and then two 11x14, if you want to work side by side.
I can't grab the idea why you would work side by side, is there a specific reason?
It would be lot easier just to work on top, and use layer groups if you want to keep different versions separated.