Just use the dichlor that PoolDoc linked above. If you use it for awhile, your CYA will build up fairly quickly. Don't run anymore CYA tests until:
1) You have added granular CYA separately and it has been a week since you have done so

OR

2) You have been using Dichlor for a week to 10 days.

Otherwise you will just be wasting your CYA testing reagents.

If you will let us know if you prefer to add CYA separately or use Dichlor which will add CYA at the same time it is adding chlorine, then we can give you a little more specific instructions.

Hope this helps.