To export specific contacts, you can use the filters to narrow down the list of contact information that you would like to export.
To do that, click on the "filter list",
Set up the criteria that you would like to filter,
Check on the clients that you would like to export and click on "EXPORT"
Select the format that you would like to export and you will be able to export the specific contacts.
However, if you want to export all the clients, you can go to the right corner right below your avatar image to "EXPORT" all the clients.