Stretching a pod to a second FlashArray means making the volumes (and other objects) that are in that pod available also on a second array. For Site Recovery Manager, it is recommended to make sure that the second array is added into the array managers before stretching the pod.
You can either stretch the pod first and then add the second array to the array managers or you can add the second array to the array managers and then stretch the pod to it.
It is generally recommended to do the second option (stretch last) this way you can be sure that SRM can still manage that pod if one of the arrays hosting the pod fails as if you make sure your first step is to update (and/or verify) the array managers prior to a stretch you are less likely to forget to do so.
So take the example a pod called testPod which is on a FlashArray called flasharray-m50-1.
This pod has a production group called testPG that replicates to flasharray-m20-1:
SRM discovers this array pair as well as the VMFS that is replicated in it:
I now want to stretch this pod to also exist on the FlashArray called flasharray-m50-2. Before I do that I need to ensure my array managers are configured appropriately.
Select the existing array pair, and choose Edit Local Array Manager from the Array Manager Pair drop down:
If flasharray-m50-2 is not listed in the local array(s) address input, add it:
Click Save. Now edit the remote array manager:
Make sure flasharray-m50-2 is added in the peer array(s) address input:
If it isn't, add it and click Save.
Now you can stretch the pod to flasharray-m50-2: