Do I add my account number in the beginning or the end for my refund does anybody know please and thank you

When you get to the end it will ask where you want your refund to go. 

Did you already e-file?  If you did NOT e-file you can go to the FILE section and change how you want to receive your refund.  If you want direct deposit you need the routing number and your own account number.

You cannot  change banking information while your return is in pending, nor can you change it after the return is accepted.  The IRS does not allow it.