You can adjust the size of your image in two ways: by either selecting the full page width option or by selecting the text width option and then dragging the bottom right corner of the image to adjust the size. Here's more on these two:

  1. Select the image on the form, and you'll see a range of formatting options above the image. Select the first option (full page width) from the menu to make the image the entire width of the page instead. The second option in the menu can also be used to make the image the same width as the rest of the form content (content width).

Full page width

Content width

  1. If you want to manually make the image smaller or larger, first ensure the image is set to content width, and then you can grab the corner handle down the bottom right of an image, and drag it to resize the image:

    Set the image to content width, and then adjust the size further using the corner handle