By default, images and contetn are left-aligned, but you can center-align, or right-align content like this:
- Add a one column "structural" block onto the form
- Click on the newly added structural block so that its selected, then click on the "Style" tab, and choose "center" under "Text Align"
- Place your image and text into this structural block. The image (and anything else you place into this structural block), will now be center or right aligned.