This article explains how to export your contacts from FreeAgent in .vcf format.
Navigate to the 'Contacts' tab at the top of the screen and select the 'Export Contacts' button at the top right.
FreeAgent will then generate a .vcf file for you to save to your computer.
Alternatively, you can use the export all data function which will give you an Excel spreadsheet of all your FreeAgent data with separate tabs for each section.