Hi Soumya ,
In order to generate a barcode with the Barcode module from the app store, you have to create a new Barcode object (using the Barcode entity within the Barcode module). As a minimum you have to provide the BarcodeType (for example EAN 13) and the EAN itself, the other attributes have default values. After this, you can either use this Barcode object in the JA_Barcode_Generate action, or the SUB_Barcode_GenerateBarcode microflow. Both will convert the provided EAN into a barcode image. The image will be stored in the Barcode object that you provided to the action (since it inherits from System.Image).
Hope this helps!
Please have a look at the app store module Barcode