When setting up message campaigns, the way you create the campaign determines whether you can add new leads later.

1. Campaigns Created Using a CSV File
If you upload a CSV file to start your campaign, you have the option to add new leads at any time. This option is perfect for those managing a list of contacts, as you can seamlessly expand your campaign as needed

2. Campaigns Created Manually via My Network
On the other hand, campaigns created by manually selecting leads from the My Network tab are more static. This option doesn’t currently support adding new leads after the campaign has been launched