Hi Madhur,
There is a t-code "MASS", in which select object type as LFA1 and execute and thereafter select "Vendor master record (withholding tax types) X - LFBW" and execute.
However point to be kept in mind is you can enter the same WHT type /WHT code. If you need to enter a different WHT code then you need to create an LSMW.
You might need to select from layout the WHT code.
Regards,
Rithin