Enter the text and choose the heading size.
Enter the font family name, check the box if it is Google hosted and choose a suitable web safe fallback font.
Set the font size, color, style and weight.
Adjust the letter spacing if necessary.
Enter a value for the radius. The larger the value the shallower the curve.
Set the radius to zero to create a circle.
Use the HTML for a non breaking space at the end of the text to create a break between the start and end of the circular text. The HTML is
Example: The text around the icon at the top right of this page is entered like this...
Wrap Text Around An Object
Checking the box will reverse the direction of a curve and turn circular text inside out. This is easier to do than describe!