Here is the procedure avoiding the down time.
You currently have replication going from A to C
You want to add the new target D
1. Install shareplex on D
2. start sp_cop on D
3 Stop post on D
4. Activate configuration on the source A with the new target information added.
5. Flush source databases.
6. After post stops due to flush on C, take a backup and restore it to the new target D
7. Start post on C
8 Run ora_setup on D
9. Run cleanup.sql on D
10. reconcile queue queuename for datasource-datadest to flush (on D)
11. Run sp_add_trigger.sql so triggers ignore shareplex user, disable cascading deletes, check constraints and scheduled jobs that perform DML on D
12. Start post on D