Istio upgrade registry to private after install


I want to upgrade registry to my private reistry. How can I do to do it after istio has been already installed on cluster ?
so basicly I want to havve the same effect as I will have after install with:
istioctl install --set --set

Am I good understand thath secret needs to be in all namespaces ?

yes, this would be a kubernetes specific thing

actually it is not k8s related as my image for service was normally downloaded from private registry. I had problem with dowloading proxy image from docker hub.
We actually found answer: