I am making some assumptions here based on what you've provided and asked.
Are you connected to a jumpbox vm where you are then trying to connect to the cluster to administer?
if so, run this to authenticate with the cluster:
az aks get-credentials --resource-group yourRG --name yourCluster
If you have a private cluster then you'll need to tunnel into the VM and then jump to the cluster where you would then authenticae with az aks get-credentials command.
Because I am unsure of your setup, then possibly you could review the following to see if it's helpful on how to setup your jumpbox to access your cluster.