@v for vendetta : i tried to find it on net and on their site FAQ but couldn't found, i will them tomorrow to check then i will post here. I have my daughter demat account with them.
Mostly other brokers allow to manage tendering for buyback using their website/portal itself but Prostocks does not have that feature. I also have my minor kids account and spoke to them earlier. You need to contact them and ask that you want to tender shares and send them an email from registered email Id with details like your account Id, share name and quantity you want to tender.
I have not tried till now, informing as per guided by their support.
Thanks @NKJ for informing. I couldn't got time today to call them and check. Tomorrow i will try. Previously in Zerodha also, it was similar way, we need to send mail for buyback tender. Later they added this in their site itself for placing buyback orders.