I'm sorry if my original post wasn't clear enough. Allow me to elaborate.
1) Press start, go to social lists, then signs
http://i.imgur.com/8za5oAG.jpg
2) Assign your marks to a hotbar
http://i.imgur.com/wuveHlx.jpg
3) Select a mob, hold down trigger
http://i.imgur.com/R8jN41O.jpg
4) Press the button you set your mark to
http://i.imgur.com/wYx9ysy.jpg
