When you are importing CSV file as File Type in the data source, you can specify the encoding charset using the Properties field on the Data Source form. Properties field can be enabled in the Data Source Form by configuring the Form Layout.
Steps are given:
Below image shows the Properties Field:
The default character set used for decoding the imported CSV file is WINDOWS-1252. See below :
Defining a specific type of encoding such as utf-8 when importing a CSV document is necessary for proper data formatting(dependent on CSV format).