Oh, okay. It's actually really simple.
On the deviation page, right underneath the "More From User" section, there's a section titled "Featured in Groups." It's right above section labeled "Details" on the right hand side of the page.
There should be a "Submit to a Group" link with a button with a plus sign in front of it. If you click on that, a pop-up window will show up. Then you click on one of the group icons in "Recent Groups" or type in the group's name in the "Type a Group Name" option. After that, just hit the submit button and you're done.