It's a spring loaded plunger in there (not a small ball) so though it can get launched or fall free, it's easier to handle.
Just remove as normal by taking the front side plate screw out. But when pulling the yoke forward, take it slow and realize that the plunger will be at the 3 o'clock position as you hold the revolver and pull the yoke forward.
As the yoke clears the frame, the plunger will be free to launch so cover with your hand/fingers as you pull it from the frame.
Sometimes you'll find the plunger missing from the misfortunes of another persons efforts at the same disassembly. Or the plunger may be stuck down in the hole flush with the yoke surface from dirt and dried oil in there.
A little coaxing with oil and the tip of a small screw driver will usually loosen it up and free it but remember it's still under spring tension.