You can import clients from a CSV file into Full Slate from Clients > List. Before importing, open the CSV file in Excel and change the columns labels to match the example that is attached. This will help ensure your client data is loaded correctly.
You can also import your clients from Google or Constant Contact. When you click the import icon on Clients > List just choose "Google" or "Constant Contact" and then log-in to your respective account to authorize us to access your client list and import them into Full Slate.