The process to place After Market Orders (AMOs) on Tickertape is exactly the same as placing an order during market hours. See this article on how to place an order.
AMO orders placed on Tickertape behave like any other AMO order i.e. they will be placed on the exchange on the next trading day.
Currently, cancelling an AMO order that has been placed is not possible through Tickertape (we're working on this). If you want to cancel a placed AMO order, please visit your broker's order-book section.