With a blog you will obviously publish content. To do with this theme is nothing different or out of the ordinary. This theme will make excerpts automatically. You have to do nothing special. That said, though, you may want to control excerpts or post mark-up like images in them.
To control your excerpts or added mark-up in them, all you have to do is use the “Optional Excerpt” textarea on your “Write Post” form in the admin. To learn more about using this box, please see Admin Post Page article, then to take it a step further, check out the posts in the Theme Usage category like Posting Images, for example.