Go on your Facebook home page
Then click on Pages Tab
From Your Pages, select the Fan Page from where you want to download leads
On the menu bar of your fan page, click on Publishing Tools
For the next step, you have to click on Lead Ad forms
Select the Form you want to download leads from
Choose a custom date range
Select lifetime as option
Click on the download button and it will download the leads in a CSV file format
Open the downloaded CSV file and start following up with your leads