AutoCAD MEP PIPING how to replace fitting?

[alex7003]

Hi,

I am trying to replace or insert a reducing PVC HUB (4"x4"x2").  

Replace: when 4" hub is selected, I click on "replace fitting" button.  The button disappears and nothing happens.

When I am trying to add a reducing hub as new object to styles, it is not showing in style pull-downs.

The reducing hub exists in a content library, how to get it and many other parts to the model?   Or add other parts to the model, like long radii PVC sanitary Wye?  

Thanks!