Hi! If you have the sixth edition of the textbook, you will not receive a separate grammar supplement. The sixth edition has a grammar, punctuation, spelling and mechanics section at the end of it. The material begins on page 719. As dhauser87 said, there's loads of English Composition material on the English & Writing space. Here's a link a resource that may help: New Resources.pdf.
Best of luck in your studies,
Rianna J.
English Instructor