Yes - you can add more leads to an active campaign at any time.

The new leads will be picked up by the campaign and contacted going forward. They join the queue and start receiving emails from the beginning of your sequence. Leads already in the campaign are not affected - they continue from wherever they are in the sequence.

Go to your campaign, open the lead list settings, and add or assign a new or updated lead list.

Leads that were already contacted in a previous list will not be emailed again if they appear in the new list - Prospi checks for duplicates automatically.