You have to take a look at the Read Me First. Btw You can just do this with lockette. Place a chest, and place a sign near to it. On the topline you write [private] leave the second line blank. on the third line a co-owner. on the fourth line a co-owner.
I think he wants a plugin where you can type /chest anywhere and get your own private chest to pop up here is a plugin I found that works. Link! It also comes with /workbench