The Alignment rule is used for precisely that; alignment. Using it, you can align graphics and text. Six positions are available; Left, Center, Right and Top, Middle, Bottom. The rule is used by selecting what you want to align and then adding the rule.
An important thing to note is that the Alignment rule respects margins. If you're ever in a position where you've aligned some graphics or text, and you don't understand why it's not aligning all the way to the edge the reason is almost certainly that you haven't set the margin to zero. We suggest you read about the Margin rule here to learn more about how to use and compose the Margin rule with other rules.