Rear end breather

[Ackattack]

I know there is supposed to be a breather tube connected to the rearend, but I don't know how to connect it.

I took the rearend apart about a year ago, and I'm getting close to putting the bed back on, so I'd like to go ahead and finish up the rearend (fluid, brake lines, etc.) before I put the bed on.

On the top of the rearend there is a hole, is there a plastic or metal piece that is supposed to go in there? It's been too long