Hi Rachel - Not sure if this has been answered yet but - let me know. Below are steps which should help:
1. Locate the image in your Content Library and Copy the Image Location URL
2. Open New or saved email
3. Insert Text box
4. Right click on Text box
5. Click on Edit Source
6 Include the following code with your own customiztions:
<img style="width:600px;height:184px;" src="<INSERT THE IMAGE URL LOCATION HERE>" alt="" width="600" height="184">
<p style="position: absolute;top:120px;width:500px;padding-left:30px;">
<font style="font-size:18px;">
<b>Lorem ipsum dolor sit amet, consectetur adipiscing elit.<br>
Sed sagittis hendrerit massa, ut cursus justo tempor eget.</b>
</font><br>
</p>
7. Click "Save"
Let me know if this Answered your question. Thanks.