Dear Raj
If you want to enter Opening Stock in tally then go to Account Info. select ledger and go to Alteration and select ledger account of Stock
In that window you can see two column one for Amount which should be value of Stock and next column is for Date. Use the date column for the date of Stock in Hand for example if yopu are entering Opening Stock the In Date column put date of st April the close the wiondow. After that you can see the opening stock in Stock Ledger account.
There are no need for using Cost center for Stock purpose