Help installing sapphire caseback

[mps354]

Hey guys, I’ve sourced a sapphire caseback for my speedmaster (I have the hesalite crystal / solid caseback). I know that in order for it to fit properly, you have to swap out the existing spacer ring for a larger one. Anyone have pics on how to do that?

I’ve gotten off the caseback, removed the dust cover, and removed the crown and stem, but I don’t know how to go about swapping the spacer.

Thanks!