This is really up to you. Of course, if you have asked to teach in a computer classroom, you probably should be using computers for more than just e-mailing assignments to your students. However, individual instructors' use of computers varies. Some TA's report using computers for little more than daily writing prompts to get classes started while others make extensive use of computers for in-class drafting, forum assignments, research, etc. The technology is there to be used, but there is no set guideline as to how much you should employ it.