To download Your Facebook Lead Ads contacts as a CSV File, take the following steps:
Step 1: Head to your Facebook Page, then click Publishing tools.
Step 2: Next click Lead Ads Forms.
Step 3: This will open the Forms Library. From here you can download the leads for any of your ongoing forms.
Import to Nimble
Click your avatar in the top right hand corner
Choose Networks & Imports
From here, use the Import Wizard to upload your file.
For more information about this feature, please take a look at the following: