I have fitted several there is no easy way to fit them:
1. Ring use tamiya tape along and across with a pin apply a drop of super glue in the open areas to fix it to the plastic body, leave for at least two hours before removing the tape.
2. Fix the mesh grill in the same way, leave two hours before removing the tape.
3. Now the cross Ring same way, including the waiting time.
4. Nut ring same as the other three stages.
If you are lucky it won't ping off over night, only use little amounts of glue as it will stick out when you paint it.
Forget the Fan on a sound loco there is no room for it.
Hope that helps?