Using a text widget in the Front Page Top 1, 2, 3, and 4 positions, here is the first one you can use as a guide. Simply replace the content and image path to your own:
<div class="post-thumbnail" style="margin-top:10px; padding:6px;"><img class="center" src="https://demo.styledthemes.com/celestial-free/wp-content/uploads/fp-responsive.jpg" alt="responsive" /></div><h3>Fully Responsive</h3><p>Celestial is a fully responsive WordPress theme for you to enjoy viewing your website in your favourite mobile device. I've incorporated the popular Twitter Bootstrap framework to give you more flexibility whether you are on a desktop or an iPhone.</p>
Repeat for each widget. To hide the widget title, check out the plugin “Remove Widget Titles”