Anywhere in your Twikey environment, you can access the import function on top of the page.
Use the button and select 'Import'.
Once selected, you'll be directed to the global import page where you can specify the type as 'Customers'. Alternatively, navigate to your customer overview and click the import button (with the customer import option already pre-selected). Then, simply indicate your desired format (CSV or Exact Online) and upload your file. Further details regarding file content are provided below.