Adding "padding" creates blank space around an image, which can be useful to separate your text from the borders of an image. To add or edit padding, click your image to select it, then click the "Insert/edit image" button, located on the WYSIWYG toolbar.  

In the pop-up window, click the "Appearance" tab, then select the "Alignment" of the image, in relation to the text (Top, Letf, Right, etc.), and enter the values for the padding in the "Vertical space" and "Horizontal space" fields, respectively. No padding is applied by default, and a value of "5" in each field is a good starting point. Click the "Update" button to apply your changes.

These steps can be repeated, with different values entered in the "Horizontal" and "Vertical" fields, until the padding appears as desired.