Release the gear that couples both lenses' focusing mechanisms (1 screw). Release the lenses (3 screws each). That's it, the front is disassembled. The Ring around the viewing lens that fell off when releasing the front plate is obviously only for holding the lens cap and not attached anywhere.

Now it's time to clean the lenses. That's a standard procedure, I won't cover it here. There are enough guides how to clean a lens without destroying it in the web.