Hi Priyanka.
Go to SPRO - Financial Accounting(new) - Contract Accounts Receivable and Payable - Basic Functions - Postings and Documents - Document - Maintain Document Assignments - Define Sales/Purchase Tax Determination. Here you will define tax code for tax code determination and make a link to the tax codes used in your tax procedure (which you can maintain via t-code FTXP).
Link between transactions and tax codes is maintained in t-code EK02. If you need to set the GL accounts to which the postings will go, use transaction FQC1.
Hope it helps.
Marko