Trying to teach kids when they are not paying attention is the number one issue I see with toddlers on the autism spectrum. I see it in the classroom environment, therapy clinics, and in the home. This is a serious issue, and in most environments parents don't have any control over what's going on. At home, it's a different story. You can overcome attention issues by playing with your kid. Use the kid's inherent motivations and likes to get them engaged in activities where you can target specific skills and language.
If your kid won't pay attention to short stories like Brown Bear Brown Bear, What Do You See?, try this flash game that will read the book to them.