Help with excerpts

I’m using WP 2.6.1 and am having trouble figuring out how to display my posts as excerpts. I’m using the Revolution theme, if that matters.

I’m new to WP, CSS, php, etc. and am quite baffled by terminology such as “the loop”, which I have yet to dive in to. Is there a simple and easy to follow tutorial or post regarding excerpts? I’d like my main and secondary pages to show all posts as excerpts.

Thanks!