Note also that you need an admin account to do this.
If your organization has requirements for custom Lead, Contact or Account fields, it may not be possible to upload business card data to Leads and Contacts. However, you can set a Fixed value for the required custom fields.
Go to the Scan to Salesforce tab, then the gear icon. Open Admin Settings and click Field settings. Then, select the object and record type. Enter a fixed value for the corresponding custom fields.
Also, if you enable Allow users to overwrite values for fields, users can individually edit custom field values when transferring business card data. See here for more information.