Glue the top two thrusters on. This is the fiddliest bit as they don't have anything to rest against. A little blob of poster putty will be your good friend here. Glue on the top two cannons, and glue a strip of staples behind the cockpit to give more body. You are done - unless you can think of some way to add an R2 unit. You can also use one of the discarded large binder bodies as a display stand.