Select Customize, and in the adjacent text field, type a unique custom field name. Custom field names cannot be the same as any of the predefined list of field names. Nor can they be the same as any other custom field name in the record.
For example, assume column 3 of your data source file consists of first names. In column 3, select Customize and in the adjacent box, type first_name.
To change the order of the fields, check the box beside the field name that you want to move, and then click Move Up or Move Down.
To add additional fields, click Add and repeat the tasks in step 1 to use a system pattern or to create your own custom field.
After you map your data source file columns, upload the data source file.