Problem filling out an area


#1

Howdy boys, I would just like to know how i fill out the part marked in red, so that it’s completely filled.


All i’ve managed to do is “put a lid on it” so to speak, where i’ve not been able to fill out anything.
The final product i’ve tried to achieve is to have a hollow sphere where i can change the width of the walls.
https://gyazo.com/1e2caaa3b7c6c86e8f0be65f46ae9c10 <= how i want to do it.


#2

English isn’t my first language so sorry if i phrased things wrong.


#3


Like the inside of the outer circle is filled. And the inside of the inner circle is empty if that makes sense.


#4

if the two dome edges are on the same plane and exploded, just trace a line over the exisitng geometry on both domes and delete the centre face.