Don't do the Image Size routine! With the image open, select the Crop tool. You can then check available Crop Presets by clicking the tool icon in the upper left corner. But if the correct aspect ratio is not in the list, then you can just enter your aspect ratio/dimensions into the Width and Length box, just the numbers (11x14 in this case) and then draw with the crop tool and it will draw a rectangle with that aspect ratio.
The Image Size dialog may or may not be useful. If you want to do a fair-size print, you could either just go with the cropped (full resolution) image, or you can use the Resize/Resample function in the Image Size dialog to set a Resolution (ppi) value at your desired print size (say, 11x14 @ 300 ppi). This can be useful if you want to do some pp in preparation for printing, using the actual "print size".
Or, if saving for the Web or other computer displaying you can also use the Image Size dialog, or the Save for Web function, just do the cropping to the proper aspect ratio first!