I have the software installed on my PC and it appears that it doesn't support resizing, only cropping. The image manipulation functions are shown when you double-click an item, but after you do that, there is no Resize function available. Therefore you have to use another app for that procedure.
The XnView alternative is quite good and offers all the necessary tools to do this. Here is the link to download it: http://xnview.software.informer.com/
