I read lots of successful stories from this forum that both of the ways you mentioned are fine. One is to fill out a new form with new TB skin test (If positive, with a new X-ray) and attach the new form to the original returned 693. The other is to fill out the new TB skin test in the new form and copy/paste the data from the old form, like wangtexiaobai.
Did CIS return your original 693 form and which center, 485 RD?