If you want to use WordArt styles from Word 2003-2007,
save your Word 2010 document as a "Word 97-2003 Document (*.doc) to access previous options.
Once the WordArt style is inserted into your document, you can then access the WordArt Tools to adjust appearance. When you have finished formatting the WordArt, you can then save your document as Word 2010 (*.docx).