Welcome to PSCS2 - which I happen to just love as my scrapping program.
To change the size of an object in CS2 you can do it a couple of ways. First, with the move tool selected and the layer of your photo selected in the layers palette, you can just drag the corners - and to keep it in correct proportions, hold down the shift key as you drag.
The other way is to use the free transform - which is located under the Edit function on the menubar. Or you can do Edit>Transform and from the flyout choose Scale. On the options bar at the top click on the link in between width and height to keep the proportions the same. Actually this locking can be done on the options bar with Free Transform also.
Here's a quick tutorial I wrote that has a screenshot of doing this with the "scrubby" feature.
Using the Scrubby in PSCS2
Hope this helps and I'm sure we'll be seeing you in the Photoshop section as you learn this wonderful program.