Im not 100% sure,but do you re thread in the bolts and use them to knock each side through?
As far as im aware its pressed in[not like a steerer but more like a hub endcap[so there might be an o-ring around each side]
I'm trying to remember, but I think if you look inside you can see where the two sides meet in the middle there's a very small gap - I inserted a screwdriver to catch the edge and gently tapped it out on both sides.