You may want to download leads you previously uploaded to a campaign for multiple reasons - perhaps you want to re-target leads who haven't opened any emails or haven't replied in your sequence (psst - you should do that if you aren't already!)
Here are the steps to download leads:
Go to the 'Leads' tab of a campaign
Use the 'Filter' button to apply your desired conditions. Learn how to apply advanced filters here.
Select individual or all leads to get the download button.
Download the selected leads.