If you want to add a text over an image/image under text, follow these steps:
Select the Text element's parent Box in the treeview on the top.
Add and set background image, using the Element Background settings in the bottom-right.
Under the image there is repeat option. Set it accordingly.
Add whatever text you like.
Adjust the padding of the Text element to position it on the image.
Add padding to the Box element (Element Position settings), so that it has enough space for your image. (Your image might get cropped otherwise.)
Let us know if you need any more help!