In order for the users to be synced they need to be part of the correct groups under the respective AEM instance. EX: If you want all users from DEV instance to be synced, first go to "adminconsole" and make sure that users are part of the respective groups under the DEV instance.
Ideally, Any user that is present under the instance profile under "adminconsole" will automatically be synced. You just need to make sure the user is assigned to right product/group
There is a User Sync Tool and when the User Sync runs, it fetches a list of users from the organization’s Active Directory and compares it with the list of users within the Admin Console. It then calls the Adobe User Management API so that the Admin Console is synchronized with the organization’s directory. The change flow is entirely one way. Any edits made in the Admin Console do not get pushed out to the directory.
Please see the link for IMS Support for Adobe Experience Manager as a Cloud Service.