Hello, @sarahsvendsen84 
Welcome to the Canvas Community! If your organization permits it, https://community.canvaslms.com/docs/DOC-26558-how-do-i-add-users-to-a-course details the process. If you aren't able to add a teacher to your course using these instructions, it most likely means that your local Canvas admin has disabled this teacher permission and is managing users on behalf of its teachers—so please contact the local Canvas admin or eLearning department for your school for additional assistance.
