You can do it if you know how! It's pretty easy.
You are not required to have the categorization project take this step.
As Richard explained, below, you add a parent. Sometimes you have to do a little research to find one, but sometimes it's obvious. This is one that takes research. You found the parent already, so you just have to open your new category's page in edit mode and add [[Category:United States Veterans Organizations]] at the top of the page, above the text.(and that's just about all the text you should have on a category page, so you did a good job keeping it short.) Then click the green SAVE PAGE at the bottom and you're done.
Give it a try, and if you have difficulty, add another comment and I'll do it. Then you can look and see what I did.