I would add css in your css file – style.css (which is apart of your theme)…or you can use a Custom css page. Check to see if you have a Custom CSS editor (some users do from the Jetpack installation).
Here is how to add a div –
<div class="alignleft">Your content goes here</div>
I used the class “alignleft” as an example, it allows you to add images or content and it will align to the left of whatever you add it next to. You can also use alignright.