HHey Boston,
Congrats on making it to the invite to DD- are you trying to accept from the "home" page? Try going to the clan wars page, in the upper left corner, click on the menu bar. At the bottom of the drop down, you should see Diamond Invitation bar,, click on it and follow the directions.Once you see the "pick your time zone" and click on it, you are enrolled in DDivision. It should be as easy as that! None of the above will work if you are not the clan commander however. Let us know when you get it to work.