Click Create New User next to Select Users. Fill in First Name, Last Name, Email and Phone (all four are required — you'll see e.g. "Empty User's Phone" if one is missing) and save. Sprwt creates the customer account with an auto-generated password (unless you supply one), marks the email as validated, sends the standard admin created your account email/notification, and selects them on the proposal. You need the Edit Users permission for this button to work; if account creation fails (e.g. the email is already registered) the error is shown in the modal.