Go to Wowhead.com. Choose Database->Itemsets->Class you want.
In the "Tag" field in the filters section at the top of the page that loads, choose "Arena Season 8 Set" and click "Apply" so you only get the Wrathful set(s) for that class.
If you have multiple sets available, choose the set you want. It should open another page with the five set items.
Click on the first one in the list, in your address bar in your browser, it should give you something like: http://www.wowhead.com/item=51503. Take the number at the end, and write it down. Do that for all the Wrathful items you want to load into Rawr.
Open Rawr, go to Tools->Edit Items and down at the bottom left hand corner click the Add button. In the window that pops up, uncheck Armory, and leave Wowhead checked. Punch in one of the numbers you wrote down and hit Ok. It should add it to your item
cache. Continue for all the numbers you wrote down.