The simplest way to add an icon to a button is to insert an inline image.
Create a button
Place the cursor where you want the icon
In the popover toolbar, click the down arrow towards the right end and select Inline Image. This will open the Media Library for you to select an image.
Click on your icon image and click the Select button
That’s all!
If you need to resize the image, just click it and a little window pops up to change the width (will automatically adjust height with the width).
