you will get mail from tcs in around two weeks after record date, then buyback dates will be mentioned, then you can tender your shares in buyback during buyback period from your broker site. For zerodha , you can check below link how to place order, for other broker, you can call and check with them how to place order for buyback. https://support.zerodha.com/category/trading-and-markets/corporate-actions/articles/how-do-i-apply-for-buy-back
I have 32 shares of TCS