Hi catherinecomeau,
I'm happy to assist you with this. First off, it looks like your front page is set to display a static page, instead of your latest blog posts. In order to achieve the same look as the Autofocus demo, your front page needs to display your latest posts.
To fix this, go to Settings > Reading in your Dashboard. Find the setting labeled "Front page displays", and select "Your latest posts". Click the "Save" button.
Next, you'll need to create some posts. I see that you don't have any posts at the moment. When you create posts and add images to them (either attachment images or featured images), Autofocus will display them on the front page. When you hover your mouse over an images, the post title and excerpt will appear on top. This is created automatically for each post. To create a new post, go to Post > Add New in your Dashboard.
I hope this helps. Let us know if you have any other questions.