Move pivot to center of this object


I search for many hour to move pivot to center of this object.
My steps are as below
Create cylinder/ cut a half/ use Zmodeler Bridge/ Zmodeler Qmesh.

I try this button but not work


press tooL>makepolymesh3d then press that icon in red you circled, looks like you was editing 1 side of the mesh making it non symmetrical


Thank for reply. I find out that just need to turn off Activate Symmetry.