If you are referring to a CSV file campaign, yes you can by importing it in Alfred dashboard.
Go to your specific campaign you want to add more leads click the three dots located at the right side of your campaign dashboard and select Details.
Once you land in this page click Upload more leads
Drag and Drop the file here
Awaiting to upload the profiles click Upload button located at the top right.
Once upload is done it will reflect on how many leads were uploaded.