Vendor & Customers in FBL3N

Hi,

I want to see Vendor/Customers in FBL3N for Sales/Purchases GL's. I'm able to see the fields in the layout but data is not displaying. is there any special settings required to get the data. I've already seen BSEG table and there KUNNR field is appearing.

Please tell me the way to appear the data for this fields.

Thanks

Swapna