The EDIT PICTURE feature allows you to do some basic editing such as Red Eye, Crop, Enhance, and rotation of your photos.
The above are probably the most convenient features for novice photographers. Standard sizes such as 4x6, 5x7, and 8x10 can be pre-selected. Or you can choose to go manual and crop each photo yourself. Red-Eye works by reducing Red Channel color. Enhance gives a little boost to Contrast and Color.
Here is where you can use Picasa's organization abilities. Name an album/folder where you want some temporary photos to go which have been cropped, and then select those photos in the album/folder for your desired export option, such as printing. In this way, you can print several of your cropped photos at one time.