This is a one-time step.
Log in to the FlashArray and go to Storage -> Hosts and click on the plus icon in the upper right corner of the Hosts panel to bring up the Create Host dialog.
Provide the name of the ESXi hosts in the cluster.
After you click on Create, this host will appear in the Hosts list.
Repeat this step to create FlashArray Host objects for all ESXi hosts in the cluster.
Go to Storage -> Hosts and click on the plus icon in the upper right corner of the Host Groups panel to bring up the Create Host Group dialog.
Give the Host Group a name.
Add all ESXi hosts to the host group just created.