If the source pod has been demoted and you promote the target pod, this process is generally called a "recovery" or a "failover". The workload has been brought down on the original site and is being brought up in a new site. To first demote a pod, refer to the instructions here:
Demoting an ActiveDR Pod in a VMware Environment
Once that is completed, the target pod can be brought online via a promotion operation.
Login to the target FlashArray and click on Storage > Pods and then identify the desired pod. Click on the respective vertical ellipsis and choose Promote.
Confirm the promotion.
This will take the latest point-in-time of the pod and refresh the volumes with the latest data set and make them read/writeable.
The pod will go into the promoting status briefly:
When completed it will have the status promoted:
Once the pod has been promoted ActiveDR will see that the source pod is demoted and automatically swap replication directions. If you look at the replica link on either site it is now replicating from the newly promoted pod back to the original source pod. There is no need to "re-establish" replication--ActiveDR does this for you.