Using Adjectives is a link I’ve just placed at the bottom of the Descriptions section of my English Themes For Beginners and Early Intermediate page. I’ve actually put several related links right after the other. They all provide simple text and audio lessons on the use of adjectives.
These lessons, and a number of other links on my site (especially in the Reading category of the English For Beginners page), all come from the Elementary Test Center of the Oswego City School District. They have hundreds of similar interactive online lessons and interactive activities. The District also has a similar site for more advanced learners.