Table With Id field in Destination Table

hi expert, i am new to SSIS, i have basic query regarding SSIS, i want to transfer my data from one Table to another,right,

scenario is that, 

in Source Table, there is no any primary key define , but in destination i want to create a primary key in my Table,

when i execute the package it  gives me error, and when i remove the primary key from destination table or creating primary key for two columns its work, so i confuese

create TAble Cust0_DW
(
 CustAccount nvarchar(20),
Name     nvarchar(100),
Company  nvarchar(4)not null primary key(CustAccount,Company),// using this i have set primary key on both column,in this case the package working, //
CustGroup nvarchar(60)

so please guide me.

Regards.