Select the images button from any of the Add Item dialogs.

The initial screen you will see looks like the following...

To add images that are already saved on your computer, click on any one of the three 'Load Image' boxes.
An Open Dialog will pop up where you can navigate to where your images are saved.

Once you select your image, click Open and your image will be loaded into the image box that you originally selected.

Once your images have been loaded, you can do some simple editing.

1 - You can use the zoom in and zoom out buttons to move in closer or move further away from the image.

2a - You can use the Brightness Control to lighten or darken the image.

2b - You can use the Contrast Control to make the colors in the image more or less distinguishable.

2c - You can use the Saturation Control to make the image more or less vivid.

3 - You can use the arrow buttons to move the image to the Right,
Left, Up, or Down.

Capture Images: Use this button to capture images using a
camera connected to your computer. Once the image has been captured, it
will automatically load into the image boxes. Find out how to capture
images here.
Reset Selected Image: After any adjustments have been made, you can use the Reset Selected Image button to get rid of any edits you have made since the Image Dialog was opened.
Reload Original Image: Use this button when you want to return to the image that your originally loaded before any adjustments have been made to it.
Remove Selected Image: Use this button to remove the currently selected image.