Even though your policy has already been published, you can still add new users to the target list.  

1. Find the required policy under Products > Policy > Policies in Progress. 
2. Under the 'Actions' column, select Options > View Policy.
3. Select the 'Target' tab.
4. Locate, and select the new users you require to be targeted.
5. Click Update Targets.
6. You will receive a validation message outlining the total number of users you are about to target; if this is correct, then select Confirm, and the new users will be targeted.