there are various ways of creating shared lists:
Flatten segments to a shared list : https://docs.oracle.com/cloud/latest/marketingcs_gs/OMCAA/Help/Segments/Tasks/SegmentFilterOperations.htm?Highlight=flat…
other ways to add contacts to shared list can be found here: https://docs.oracle.com/cloud/latest/marketingcs_gs/OMCAA/Help/SharedLists/Tasks/AddContactsToASharedList.htm?Highlight=…
the first option mentioned is the campaign canvas/ program canvas' add to shared list step.
Hope this helps.
Shared lists can be created when ever email have been sent out to the segmented members.
I would suggest is adding another step in the campaign canvas after the email step. This step would be moving all the contacts who have received the email to the shared list.
To delete contacts from Eloqua.
1)You can create a segment which matches the criteria for contacts to be deleted.
2)Use a campaign canvas to and move them to a shared list.
3)Use the program builder feature to delete the contacts present in the shared list. This program builder will dedupe the contacts among themselves using handler sets and process them through the program builder for the deletion.
I hope this will be helpful to you.