UPDATE – since a recent app version update, Facebook removed the contacts sync options from iOS and Android. It only allows you to upload new contacts to Facebook but does not have an option to sync contacts back to your phone.
To use your Facebook contacts with Covve you can export them from Facebook and import them into the address book that you have linked with Covve (Gmail, Exchange, iCloud or Outlook). These will synchronize with Covve.
Facebook doesn't support export of your friends list. There are however a couple of workarounds:
a) If you have (or want to create) a Yahoo! account you can use the technique described here
b) Alternatively there are some Facebook Apps that enable you to export your friends. You can search for these on Facebook.
Instructions on how to import your contacts can be found:
a) Here for Gmail
b) Here for Exchange/Outlook
c) Here for Office365