Create a path in the shape you want (circle) and use the text on a path option.
You can fill this text just like any other.
To create new text and fit it to a path:
Use the vector drawing tools to create a vector shape.
Click the Text tool .
In the Tool Options palette's Create as drop-list, choose Vector.
Select other options (font, size, alignment and so on) as desired. Use the Materials palette to set the text's Background/Fill property as well as its Foreground/Stroke property.
Move the cursor over the line or shape until the cursor changes to , and then click. The Text Entry dialogue displays.
Note: To place text on a vector object or path without attaching to the object or path, hold down the Alt key and click.
Enter the text and click OK. The text displays along the path of the shape.